OF 

HYSIOLOGY 

Ritchie 


UC-NRLF 


GIFT   OF 


BIOLOGY 

UBftAJtY 

6 


NEW-  WORLD  HEALTH 
BOOK  //A,'' 


PRIMER  OF 
PHYSIOLOGY 

BEING  A  PRACTICAL  TEXTBOOK 

OF  PHYSIOLOGICAL  PRINCIPLES  AND 

THEIR  APPLICATIONS  TO  PROBLEMS 

OF   HEALTH 


BY 


JOHN  W.  RITCHIE 

EDITOR  OF  NEW-WORLD  SCIENCE  SERIES;     JOINT  AUTHOR  OF 
NEW-WORLD   HEALTH  SERIES 


Illustrated  by 

EARL  HORTER 

HERMANN  HEYER 

HARRY  FREEMAN 

1920  REVISION 


YONKERS-ON-HUDSON,    NEW    YORK 

WORLD     BOOK     COMPANY 
1920 


WORLD  BOOK  COMPANY 

THElHOCJSE     OF    APPLIED     KNOWLEDGE  gjQLOGY 
Established,  1905,  by  Caspar  W.  Hodgson 

YONKERS-ON-HUDSON,  NEW  YORK 
2126   PRAIRIE    AVENUE,   CHICAGO 


"  Our  national  health  is  physically  our 
greatest  asset.  To  prevent  any  possible 
deterioration  of  the  American  stock  should 
be  a  national  ambition."  These  words  of 
Theodore  Roosevelt  express  the  idea  that 
has  actuated  authors  and  publisher  of  New- 
World  Health  Series.  The  texts  explain 
the  means  by  which  young  Americans  can 
lay  the  foundations  for  sane  and  vigorous 
lives.  They  stand  preeminent  among  Books 
That  Apply  the  World's  Knowledge  to  the 
World's  Needs.  This,  the  third  book,  com- 
pletes the  series  for  elementary  schools  and 
teaches  health  conservation  through  prac- 
tical applications  to  daily  life  of  modern 
hygiene  based  on  physiological  principles. 
The  conservation  of  individual  and  national 
health  is  the  purpose  of  the  series 


Gift 


KWHSIRP  OF  P-I? 


Copyright,  1913,  1917,  1920,  by  World  Book  Company 

Copyright  in  Great  Britain 

All  lights  reserved 


PREFACE 

IN  this  last  volume  of  a  series  of  elementary  school  texts,  the 
author  has  attempted  to  give  the  pupil  a  general  idea  of  the 
plan  and  working  of  his  body  ;  to  make  plain  to  him  the  pos- 
sibilities of  health  ;  and  to  point  out  the  paths  that  lead  to  the 
realization  of  these  possibilities.  In  how  far  the  attempt  has 
been  successful,  the  contents  of  the  book  itself  must  decide ; 
a  preface  can  neither  make  nor  mar  that  which  is  already 
written.  On  three  points,  however,  the  writer  will  venture  a 
word  that  may  make  clear  the  point  of  view  of  both  this  volume 
and  the  series  of  which  it  is  a  part. 

In  the  preparation  of  the  series  the  matter  relating  to  in- 
fectious diseases  has  been  given  a  separate  volume,  Primer  of 
Sanitation,  but  only  to  a  measured  extent  has  it  seemed 
advisable  to  attempt  a  division  of  topics  between  the  present 
volume  and  the  first  book  of  the  series,  Primer  of  Hygiene.  The 
fact  that  many  children  leave  school  at  an  early  age  seems  to 
demand  that  an  elementary  course,  including  that  which  is  of 
most  value  in  the  field  of  personal  hygiene  and  complete  within 
itself,  be  given  in  the  lower  grades.  The  fact  that  this  arrange- 
ment is  necessary  is  no  misfortune,  however ;  for  in  the  teaching 
of  physiology  and  hygiene,  as  in  the  teaching  of  arithmetic, 
grammar,  and  geography,  the  best  results  are  obtained  by 
making  a  general  study  of  the  whole  subject  before  more 
detailed  work  is  taken  up  in  any  particular  field.  It  is  believed 
that  the  introduction  of  new  and  different  subject-matter  and 
the  treatment  from  the  physiological  point  of  view  will  prevent 
any  feeling  of  repetition  when  topics  that  have  been  studied  in 
Primer  of  Hygiene  are  again  taken  up  in  this  volume. 

The  author  believes  that  hygiene  is  best  taught  by  giving  a 
solid  basis  of  structure  and  function  for  it.  He  has  little  confi- 
dence in  get-wise-quick  methods  in  any  subject,  and  he  has  not 
hesitated  to  include  in  this  volume  sufficient  physiology,  with 
the  anatomy  that  is  needed  to  make  it  intelligible,  to  give  an 
outline  knowledge  of  the  human  mechanism.  At  the  same 
time,  the  attempt  has  been  made  to  select  for  treatment,  from 
the  vast  field  of  physiology,  topics  that  have  direct  and  vital 


515607 


iv          '  '"   '.';".    '  /.      '^PREFACE 

hygienic  applications,  —  to  teach  hygiene  through  the  modern 
physiology  that  lies  behind  it,  rather  than  to  teach  hygiene  by 
rule-of-thumb  methods  or  to  teach  physiology  for  its  own  sake. 
It  has  been  thought  best  at  times  to  go  somewhat  far  afield 
with  the  hope  of  widening  the  pupil's  hygienic  horizon ;  for  the 
world  is  filled  with  people  who  for  lack  of  a  few  large  ideas  are 
unable  to  use  the  many  small  ones  that  they  have  accumulated. 

With  the  idea  that  children  ought  not  to  be  taught  the  matter 
that  is  in  a  book  of  this  kind  because  it  may  bring  into  their 
minds  thoughts  of  sickness,  the  author  is,  of  course,  not  in 
agreement.  The  real  and  vivid  ideas  of  disease  that  are  in  the 
minds  of  children  come  not  from  books,  but  from  personal  ex- 
perience on  beds  of  sickness  ;  from  first-hand  knowledge  of  the 
suffering  of  disease-stricken  parents,  brothers,  and  sisters ;  and 
from  the  sudden  vanishing  of  playmates  and  friends.  As  long 
as  disease  is  in  the  lives  of  children,  it  will  be  in  their  minds, 
and  the  way  to  put  it  out  of  their  minds  is  to  banish  it  from 
their  lives.  The  author  has  done  his  part  in  the  writing  of  this 
series  of  books  with  the  hope  that  they  would  do  something  to 
bring  sunshine  and  happiness  into  the  lives  of  the  children  that 
now  are  and  are  yet  to  be.  He  believes  that  modern  hygienic 
knowledge  is  able  to  free  our  people  from  most  of  their  illnesses, 
and  that, this  knowledge  ought  to  be  given  to  the  people  by  the 
schools  that  have  been  founded  for  their  instruction. 

The  author  wishes  to  thank  all  those  who  have  assisted  him 
during  the  preparation  of  this  work  and  to  acknowledge  specifi- 
cally his  obligation  to  the  following  gentlemen,  each  of  whom 
has  read  all  or  part  of  the  proof:  Professor  J.  S.  Caldwell, 
Dr.  F.  B.  Dresslar,  Dr.  Graham  Lusk,  and  especially,  Dr. 
Martin  H.  Fischer.  For  the  point  of  view  of  the  book,  how- 
ever, and  for  any  errors  that  may  be  in  it,  the  author  alone  is 
responsible. 


CONTENTS 

CHAPTER  PAGE 

I.    THE  POSSIBILITIES  OF  GOOD  HEALTH         .        .  i 
II.    THE  HUMAN  BODY  AND  THE   CELLS  OF  WHICH 

IT  is  BUILT 7 

III.  THE  FRAMEWORK  OF  THE  BODY          .        .         .  16 

IV.  THE  MUSCLES  AND  THE  CARRIAGE  OF  THE  BODY  26 
V.    THE  HEART  AND  THE  CIRCULATION  OF  THE  BLOOD  39 

VI.  RESPIRATION 53 

VII.  VENTILATION 60 

VIII.  ADENOIDS  AND  COLDS 70 

IX.  CLOTHING  AND  THE  BODY  HEAT         ...  83 

X.  THE  NERVOUS  SYSTEM 91 

XI.  THE  CARE  OF  THE  NERVOUS  SYSTEM          .        .  102 

XII.  THE  EYE .        .109 

XIII.  THE  EAR 122 

XIV.  THE  ORGANS  OF  TOUCH,  TASTE,  AND  SMELL      .  129 

XV.      FOODS  AND   WHY   WE   NEED   THEM          .  .  .135 

XVI.  THE  DIGESTIVE  ORGANS  AND  THEIR  WORK         .     145 

XVII.  THE  FOODS  WITHIN  THE  BODY    .        .        .        .158 

XVIII.  FOODS  AND  HEALTH 166 

XIX.  THE  TEETH 183 

XX.  TOBACCO 197 

XXI.  ALCOHOL       .        .        .        .        .        .        .        .210 

XXII.  ACCIDENTS 221^ 

XXIII.  REALIZING  HEALTH  POSSIBILITIES       .        .        .    233 

APPENDIX .243 

PRONOUNCING   GLOSSARY 246 

INDEX  .  247 


We  suffer  from  disease  because  of  ignorance  5 
we  escape  it  through  knowledge. 

—  RICHARDS. 


CHAPTER  ONE 

THE  POSSIBILITIES   OF  GOOD  HEALTH 


FIG.  i.    The  length  of  time  a  top  will  spin  depends  on  the  conditions  under 
which  the  spinning  is  done. 

THREE  boys  at  the  same  time  threw  their  tops  into  a 
ring  drawn  on  the  earth.  One  top  struck  a  pebble, 
bounded  into  the  air,  and  fell  motionless  on  its  side. 
Another  top  worked  its  way  into  a  little  sandy  hollow 
in  the  earth,  and  in  thirty  seconds  its  spinning  was  over. 
The  third  top  settled  down  on  the  smooth  earth  and 
continued  to  spin  steadily  and  quietly  for  more  than  a 
minute. 

How  long  will  a  top  spin  ?  It  is  not  possible  to  answer 
this  question  definitely  because  the  length  of  time  it  will 
spin  depends  on  the  conditions  under  which  the  spinning 
is  done. 

Length  of  human  life  dependent  on  the  care  that  is 
given  the  body.  In  Europe  three  hundred  years  ago, 
the  average  human  life  was  twenty  years ;  today  it  is 


PRIMER   OF  PHYSIOLOGY 


Sweden 


Massachusetts 


Europe 


India 


forty  years.  At  the  present  time  it  is  in  India  twenty- 
four  years  and  in  Sweden  fifty-two  years.  In  New  York 
City  twelve  years  have  been  added  to  the  average  life 
since  1866,  and  in  Indiana  from  1900  to  1910  human 
life  lengthened  at  the  rate  of  six  months  each  year. 

During  this  period,  therefore, 
the  people  of  Indiana  may 
be  said  to  have  won  back 
one-half  the  time  that  the 
passage  of  the  years  took 
from  them. 

There  is  a  common  idea  that 
the  body  has  a  certain  "  nat- 
ural "  lifetime.  ,  The  facts 
show  that  this  idea  is  incor- 
rect. The  engine  of  an  auto- 
mobile wears  out  in  a  month 
if  it  is  neglected,  and  it  lasts 
for  years  if  it  is  given  proper 
care.  The  human  machine 
likewise  has  no  definite  length 
of  life.  It  may  be  destroyed 
in  its  first  month  by  impure 
milk ;  it  may  suddenly  be 
wrecked  by  the  germs  of 
typhoid  fever  after  it  has  been  running  smoothly  for 
twenty-five  years ;  or,  if  properly  cared  for,  it  may  give 
good  service  for  sixty,  seventy,  or  even  eighty  years.  A 
top  spins  longer  on  a  smooth  than  on  a  rough  surface ; 
an  automobile  lasts  longer  when  it  is  given  proper  care 
than  when  it  receives  rough  treatment;  and  human  life 
is  longer  when  the  body  lives  and  works  under  favor- 


52yrs.  45yrs.  4oyrs.  24  yrs. 
FlG.  2.  A  diagram  showing  the 
average  length  of  life  in  different 
parts  of  the  world."  The  length  of 
time  the  human  body  lasts  depends 
on  the  care  that  it  receives. 


THE  POSSIBILITIES  OF  GOOD  HEALTH 


Spain 


able  conditions  than  it  is  when  the  body  is  neglected 
and  abused. 

The  possibilities  of  preventing  sickness.  In  India, 
where  the  people  live  under  bad  sanitary  conditions, 
there  is  a  daily  average  of  India 
eighty-four  sick  persons  for 
each  one  thousand  of  popula- 
tion. In  Spain,  for  each  one 
thousand  inhabitants  the  daily 
average  is  fifty-six ;  in  the 
United  States  it  is  thirty ;  and 
in  New  Zealand  it  is  nineteen. 
In  five  of  the  largest  Euro- 
pean cities,  in  the  year 
1880,  the  daily  average  of  sick 
persons  was  fifty-five  for  each 
one  thousand  inhabitants;  by 
1909  this  average  had  fallen 
to  thirty-one.  In  the  United 
States  there  is  still  much  pre- 
ventable illness,  but  the  sick- 
ness among  us  decreased  23 
per '  cent  between  the  years 
1890  and  1909. 


United  States 


I      New 
Zealand 


84  56  30  19 

FIG.  3.    A  diagram  showing  the 
average  daily  number  of  sick  per- 
sons per  looo  inhabitants  in  dif- 
These    facts    prove    that    the    ferent  countries.     The  amount  of 
...  .         ,.._          sickness  in  any  country  depends 

amount    of     Sickness     in     differ-    to  a  great  extent  on  the  degree  of 

ent  countries  depends  on  the  intelligence  its  people  use  in  deal- 
degree  Of  intelligence  that  the  ^g  with  matters  of  health. 

people  use  in  dealing  with  matters  of  health.  They  show 
that  each  community  has  it  largely  in  its  own  power  to 
decide  how  many  of  its  people  shall  each  day  be  sick 
and  how  many  of  them  shall  be  in  health. 


PRIMER   OF  PHYSIOLOGY 


Disease  prevails  because  of  ignorance.      In  our  own 

country  there  are  at  all  times  1,500,000  persons  seriously 
ill  with  preventable  diseases.  This  means  that  each 
year  we  have  1,500,000  years  of  unnecessary  sickness 
among  us.  Why  do  people  undergo  all  this  suffering  if 
it  is  possible  to  escape  it  ?  It  is  because  there  still  lin- 
gers in  the  common 
mind  the  age-old  idea 
that  disease  is  an  unes- 
6  capable  thing  sent  upon 

34  us  by  the   Fates,    and 

that   health   comes    be- 

27  26  cause  of  good    fortune 

and  not  because   it    is 
deserved  or  earned. 

We  now  know  that 
this  belief  is  incorrect ; 
that  if  men  are  willing 
to  work  for  health  and 
to  earn  it,  they  may,  in 
the  great  majority  of 


o 

II 


}      t  f      . 

J    J 


1906  1907  1908  1909  1910  1911  1912  1913 

FIG.  4.    A  diagram  showing  the  number  of 

typhoid  fever  cases  in  Williamsburg,  Virginia, 

from  1906  to  1913.    In  1911  the  closets  were  real  Causes  of  most  dlS- 

screened,  so  that  flies  could  not  carry  typhoid  gaSCS     have     been      dis- 

germs  about  the  town. 

covered;    the  methods 

of  preventing  them  have  been  worked  out.  Some  of 
these  discoveries  we  are  taking  advantage  of,  but  many 
of  them  are  not  understood  by  the  people,  and  as  yet 
there  is  not  a  community  in  the  world  that  will  allow 
its  health  officers  and  physicians  to  use  all  their  knowl- 
edge in  the  prevention  of  disease.  The  ancient  Greeks 


THE  POSSIBILITIES  OF  GO&D   HEALTH 


5 


taught  that  knowledge  is  virtue  and  ignorance  is  sin. 
The  great  sin  in  the  hygienic  world  today  is  ignorance, 
and  we  are  punished  for  this  ignorance  by  the  prevent- 
able illness  that  is  among  us. 

Learning  to  keep  the  laws  of  life.  Cut  your  finger  and 
you  will  suffer  ;  burn  your  hand  and  you  will  smart  for  it. 
Observe  the  laws  under  which  your  body  lives  and  you 


FIGS.  5  and  6.  Louis  Cornaro  and  Alexander  the  Great.  Alexander,  a  daring 
and  all-conquering  warrior  of  the  ancient  world,  died  at  the  age  of  33  because 
he  paid  no  attention  to  his  health.  Cornaro,  who  was  an  Italian  nobleman, 
lived  from  1464  to  1566  — 102  years.  When  he  was  40  years  old  he  was  told  by 
his  physicians  that  he  would  die,  but  he  gave  great  attention  to  hygiene,  regained 
his  health,  and  lived  to  enjoy  a  life  of  profit  to  himself  and  others. 

will  enjoy  health;  break  them  and  you  must  bear  the 
punishment.  Whether  you  like  these  laws  or  not  has 
nothing  to  do  with  the  question.  You  did  not  make 
them ;  you  cannot  change  them.  All  that  you  can  do  is 
to  find  out  what  they  are  and  then  obey  them.  As  you  go 
through  life,  you  will  doubtless  find  certain  persons  who 
do  not  wish  to  recognize  the  existence  of  these  laws  and 
who  are  trying  to  find  some  means  of  escaping  from 
them.  This  is  impossible  ;  for  Nature's  decrees  are  un- 
yielding and  unchangeable.  The  sensible  course,  there- 


6  PRIMER   OF  PHYSIOLOGY 

fore,  is  to  listen  to  the  commands  of  Nature,  to  learn  her 
laws  and  give  obedience  to  them.  In  this  book  we  shall 
study  the  human  body  and  the  laws  of  its  life. 

QUESTIONS 

What  was  the  average  length  of  life  in  Europe  300  years 
ago?  What  is  the  average  length  of  life  at  the  present  time 
in  India?  in  Sweden?  In  New  York  City  how  much  has  been 
added  to  the  average  life  since  1866  ?  How  rapidly  was  life 
lengthened  in  Indiana  from  1900  to  1910  ?  Is  there  a  "  nat- 
ural "  lifetime  for  the  body?  Give  a  reason  for  your  answer. 
How  many  persons  are  sick  each  day  for  each  1000  inhabitants 
in  India?  in  Spain?  in  the  United  States?  in  New  Zealand? 

How  much  has  sickness  decreased  in  certain  European 
cities  during  the  last  30  years?  in  the  United  -States  during 
the  last  20  years?  How  much  preventable  illness  is  there  in 
the  United  States  each  year?  Why  do  people  allow  this 
sickness  among  them?  What  result  follows  the  keeping  of 
Nature's  laws?  What  is  the  result  of  breaking  these  laws  ? 
What  course  should  we  pursue  with  regard  to  them  ? 

SUGGESTIONS   TO  THE   TEACHER 

Keep  before  the  class  at  all  times  the  idea  that  health  is  the  nor- 
mal condition  of  the  body  and  that  disease  is  in  the  main  prevent- 
able. Make  the  pupils  realize  that  health  conservation  has  ceased  to 
be  a  scientific  problem  and  has  become  a  social  and  educational  prob- 
lem ;  that  science  has  pointed  out  how  to  save  annually  in  the 
United  States  600,000  lives  and  how  to  prevent  most  of  the  sickness 
from  which  we  suffer. 

Secure  from  local  city  and  state  boards  of  health  whatever  vital 
statistics  are  available  and  point  out  the  great  number  of  deaths 
occurring  locally  from  preventable  diseases.  For  suggestions  as  to 
additional  material  that  may  be  used  with  this  chapter,  see  page  15. 


CHAPTER   TWO 


THE  HUMAN  BODY  AND  THE  CELLS  OF  WHICH  IT  IS  BUILT 

HAVE  you  ever  watched  a  little  plant  push  its  way 
out  of  a  seed,  thrust  its  roots  downward  into  the  earth, 
and  unfold  its  leaves  to  the  light  ?  And  have  you  seen 
such  a  plant  grow  larger  day  by  day,  until  finally  it  blos- 
somed and  bore  seeds  like  the  parent  seed  from  which 
it  grew  ?  If  you 
have  worked  in  a 
garden  and  un- 
derstand plants, 
you  must  often 
have  thought  that 
they  are  very 
much  like  the 
people  about  us  in 
the  way  they  grow 

,  .  .  FIG.  7.    The  life  cycle  of  the  bean. 

and    go    through 

the  cycle  of  their  lives.  This  is  indeed  the  truth, 
and,  in  order  that  you  may  better  understand  your 
own  bodies,  we  shall  begin  this  chapter  by  learning 
something  of  the  structure  of  a  plant  and  of  how  a 
plant  grows. 

A  plant  composed  of  cells.  If  you  could  examine 
a  small  portion  of  a  leaf  or  other  living  part  of 
a  plant  under  a  microscope,  you  would  find  that  it 
is  composed  of  little  parts  built  together,  as  stones 
are  built  together  to  make  a  wall.  The  little  parts 
of  which  the  plant  is  built  are  called  cells.  Each 
cell  is  composed  of  a  half-liquid  living  material, 
which  is  inclosed  by  a  cell  wall.  In  the  center  of 
the  living  matter  is  a  denser  portion,  which  is  called 

7 


8 


PRIMER   OF  PHYSIOLOGY 


the  nucleus.     All  the  living  parts  of  a  plant  are  com- 
posed of  cells. 

How  the  young  plant  starts  from  a  cell  called  the  egg. 
Break  open  a  seed  and  you  will  find  in  it  a  young  plant. 
Where  did  it  come  from  ?  It  grew  from  a  cell  called 
the  egg.  This  cell  at  first  is  like  the  other  cells  of 
which  the  seed  is  built,  but  at  a  certain  time  it  increases 


FIG.  8.  Cells  from  the  liver,  as 
seen  under  a  microscope,  highly 
magnified. 


FIG.  9.  Cells  drawn  diagrammat- 
ically  to  show  the  spaces  among 
them,  highly  magnified. 


in  size  and  gathers  to  itself  a  rich  food  supply.  It  then 
begins  to  divide,  and  from  it  the  new  plant  comes.  Be- 
fore we  begin  the  story  of  its  growth,  however,  there  are 
some  .other  things  that  it  is  well  for  us  to  understand. 

The  parts  of  a  flower.  Examine  almost  any  common 
flower,  and  you  will  have  no  trouble  in  recognizing  the 
parts  shown  in  Figure  n.  First  come 
the  little  green  sepals,  then  the  bright- 
colored  petals,  next  the  stamens,  and  in 
the  center  one  or  more  pistils.  The 
lower  part  of  the  pistil  contains  the  young 
seeds  and  becomes  the  seed  pod.  In  the 
heads  of  the  stamens  is  a  fine,  powdery 
substance  called  pollen.  When  we  ex- 
amine pollen  under  a  microscope,  we  see  that  it  is 
composed  of  a  great  number  of  little  grains.  Each 


FIG.  10.  A  pine 
seed  cut  open  to 
show  the  young 
plant  in  it. 


THE  HUMAN  BODY  AND  ITS  CELLS 


stamen 
petal 
pistil 
sepal 


little  grain  is,  in  reality,  a  cell;    each  contains  living 
matter  and  a  nucleus,  as  do  other  cells. 

The  egg  fertilized  by  the  pollen.  Bees  visit  flowers 
for  the  nectar  that  is  in  the  blossoms  and  for  the  pollen, 
which  they  gather  and 
mix  with  honey  in  mak- 
ing "  bee  bread  "  for 
their  young.  In  pass- 
ing into  a  flower  and 
out  of  it,  a  bee  often 
leaves  pollen  on  the 
sticky  outer  end  of  the 
pistil.  When  a  pollen 

grain   is    thus   left   On    a      FIG.  n.    The  parts  of  a  flower.    To  the 

pistil,    a    long,   thread.    ?££5g2T**^" 

like    tube     grows     out 

from  it,  makes  its  way  down  through  the  pistil  to  a  young 

seed,    enters    the   seed,    and  finds   the  egg  (Fig.    13). 

Then  a  nucleus  from  the  pollen  grain  passes  out  of  the 
tube  and  unites  with  the  nucleus  of 
the  egg.  The  uniting  of  the  nucleus 
of  the  pollen  grain  with  the  nucleus 
of  the  egg  is  called  fertilization,  and 
\  is  said  to  be  fertilized,  be- 

is  shown  growing  out  cause  in  some  way  it  is  given  the 
power  to  grow  and  make  a  new  plant.1 
The  growth  of  the  egg  into  a  new  plant.  After  the 

egg  is  fertilized,  it  begins  to  grow.    In  a  very  short  time 

1  When  the  pollen  is  washed  away  by  rains,  or  when  the  spring  is  so 
cold  and  wet  that  bees  and  other  insects  cannot  visit  the  flowers,  the  straw- 
berry, plum,  peach,  and  cherry  crops  fail.  Without  the  pollen  the  eggs  in 
the  young  seeds  do  not  grow,  the  seeds  die,  and  the  fruit  drops  off. 


FlG.  12.     Pollen  grains.      , 
On  the  left  a  pollen  tube    t 


IO 


PRIMER    OF  PHYSIOLOGY 


pollen 
grain 

pollen 
tube 


it  divides  into  two  cells.  Each  of  these  again  divides, 
making  four  cells,  and  the  process  goes  on  until  there 
is  a  group  of  many  cells,  which 
have  come  from  the  dividing  of 
the  egg.  From  these  cells  are 
formed  the  roots,  the  stem,  the 
leaves,  and  the  other  parts  of  the 
new  plant.  The  outer  ones  change 
into  skin  or  bark  to  protect  the 
delicate  living  cells  within.  Some 
change  into  long  wooden  vessels 
to  carry  water  from  the  earth  up 
to  the  leaves ;  some  form  vessels 
for  carrying  food  throughout  the 
plant ;  and  other  cells  take  up 
all  the  different  kinds  of  work 
that  must  be  done  within  the 
plant.  Usually  the  little  plant 


FIG.  13.  Diagram  show- 
ing how  the  pollen  tube 
passes  down  through  the 
pistil  to  the  egg. 


stops  at  a  certain  stage  of  growth  and  rests  within 
the  seed  until  the  warmth  of  the  next  spring  stirs 
the  cells  into  renewed  activity  and  calls  the  plant 
forth  to  a  new  life. 


c  D 

FlG.  14.  Four  stages  in  the  development  of  the  young  plant  from  the  egg.  A 
represents  the  egg,  B  shows  the  division  into  two  cells,  and  C  and  D  are  later 
stages.  In  two  of  the  cells  in  C,  the  nuclei  have  divided,  but  the  new  cell  walls 
have  not  yet  been  formed. 


THE  HUMAN  BODY  AND  ITS  CELLS 


II 


The  growth  of  the  human  body  from  a  single  cell. 

The  human  body,  like  the  body  of  a  plant,  starts  from 
one  cell.  This  cell  divides  and  re-divides  until  it  forms 
a  great  cluster  of  thousands  of  cells.  Of  these  cells 
all  the  organs  and  parts  of  the  body  are  built.  Some 
cells  build  lime  around  themselves  and  form  the  bones. 
Some  build  a  great  network 
of  tough  fibers,  called  con- 
nective tissue  fibers,  which 
hold  all  the  body  together. 
Other  cells  make  up  the 
muscles ;  certain  cells  form 
organs  for  digesting  the 
food ;  the  outermost  ones 
make  for  the  body  a  tough 
covering  which  we  call  the 
skin;  a  great  group  in  the  FlGS ;  and  l6>  In'its  first  stage 

head    and    along    the    back     connective  tissue  is  a  group  of  cells 

become  the  brain  and  nerv- 
ous system ;  and  still  other    15. 
cells  become  fitted  for  doing 

all  the  Other  kinds  of  Work     framework  of  connective  tissue  runs, 

that  must  be  done  in   the 

body.      Thus  we   see   that 

the  human  body,  like  the  bodies  of   all  living  things, 

whether  they  be  plants  or  animals,  starts  with  a  single 

cell ;  and  that  when  the  body  is  grown,  all  its  parts  are 

composed  of  cells,  or  of  supporting  substances,  like  bone 

or  connective  tissue  fibers,  that  the  cells  have  built. 

The  cells  alive.  You  will  now  understand  that  if  you 
could  examine  with  a  microscope  a  small  portion  of  the 
heart,  the  liver,  or  the  brain,  you  would  find  it  com- 


This  material  hardens  into  the 


cells>  °r§ans'  and  tissues 


12 


PRIMER   OF  PHYSIOLOGY 


posed  "of  a  multitude  of  small  cells.  You  will  under- 
stand also  that  each  of  the  four  hundred  thousand 
million  cells  that  are  estimated  to  be  in  the  human 
body  is  alive;  that  each  must  have  food  and  oxygen 
and  all  the  things  that  the  body  as  a  whole  needs  ; 
that  the  life  of  the  body  is  the  sum  of  the  life  of  all 
its  cells.  When  we  study  how  to  keep  the  body  in 
health,  therefore,  we  are  only  study- 
ing how  to  keep  the  cells  in  health  ; 
for  health  means  that  the  cells  are 
in  good  condition,  and  sickness 

i^j   /      means  that  there  is  trouble  among 
/     ;^^JL^/   the  delicate  little  parts  of  which  the 
body  is  built. 

The  cells  bathed  by  lymph.  We 
have  said  that  the  cells  of  the  body 
are  built  together  as  stones  are  built 

FIGS.  17  and  18.    On  the  a   walL       YOU   Would    not,    how- 


right  is  shown  a  nerve  cell 

from  the  brain;  on  the  ever,   have   a   correct   idea   of    the 
left,  a  muscle  cell  from   structure  of  the  body  if  you  did  not 

the  stomach.  J 

understand  that  all  among  our  cells 
there  are  spaces  and  openings,  and  that  these  crevices 
are  filled  with  a  liquid  which  escapes  from  the  blood. 
This  liquid  is  called  the  lymph,  and  the  cells  are  sur- 
rounded by  it  and  bathed  in  it,  as  a  fish  is  bathed  in  the 
water  in  which  it  swims.  Only  to  a  very  limited  extent 
is  it  true  that  we  are  dry-land  animals  ;  for  the  living 
parts  of  our  bodies  spend  their  lives  under  water  as 
truly  as  do  the  fishes  of  the  sea. 

Pure  lymph  necessary  to  the  health  of  the  cells.  If 
you  had  hundreds  of  small  fish  in  a  pail  of  water,  you 
would  be  compelled  to  take  great  care  in  keeping  the 


THE  HUMAN  BODY  AND  ITS  CELLS  13 

water  fresh  and^in  feeding  them,  lest  they  should  die. 
So  with  the  cells  crowded  together  as  they  are  in  our 
bodies,  it  is  necessary  to  keep  the  lymph  pure  and  clean 
and  to  supply  it  with  the  food  and  oxygen  that  the  cells 
need.  We  therefore  have  a  stomach  and  other  organs 
for  preparing  food  for  the  cells ;  we  have  lungs  for 
taking  in  oxygen  and  for  breathing  out  the  waste  car- 


FlG.  19.     As  clean  water  is  necessary  for  the  health  of  the  fish,  so  is  pure 
lymph  necessary  for  the  health  of  the  cells. 

bon  dioxid;  we  have  kidneys  for  taking  other  poison- 
ous wastes  out  of  the  body ;  and  we  have  many  other 
organs,  each  of  which  does  its  part  in  keeping  the 
lymph  rich  and  pure  for  the  cells.  When  these  organs 
do  their  work,  our  cells  are  like  fishes  living  in  pure, 
clean  water  where  there  is  an  abundance  of  food,  and 
we  are  strong  and  well.  If  any  organ  fails  in  its  work, 
either  the  cells  will  lack  something  that  they  need  or 
the  lymph  in  which  they  live  will  become  impure,  and 
the  body  will  fall  ill.  Pure  and  rich  lymph  is  necessary 
for  the  health  of  the  cells. 


14  PRIMER   OF  PHYSIOLOGY 

Keeping  the  human  machine  in  repair.  From  what 
you  have  now  learned,  you  will  understand  that  your 
body  is  a  machine  of  many  parts.  You  will  understand 
also  that  you  are  in  charge  of  this  machine,  and  that 
the  length  of  time  it  will  last  and  the  amount  of  time  it 
will  be  laid  up  for  repairs  depend  on  the  care  that  you 
give  it.  In  this  book  we  shall  study  how  the  body  is 
built  and  how  it  works  ;  for  no  one  can  care  intelligently 
for  a  machine  that  he  does  not  understand. 

QUESTIONS 

Of  what  is  a  plant  composed?  Describe  a  cell.  Where 
does  the  young  plant  within  a  seed  come  from?  Name  the 
parts  of  a  flower.  What  is  pollen?  Why  do  bees  visit  flowers? 
What  do  they  do  for  flowers?  What  grows  from  the  pollen 
grain  when  it  is  placed  on  the  pistil?  What  is  fertilization? 
Describe  the  growth  of  the  egg. 

From  what  does  the  human  body  start?  Of  what  are  all  the 
organs  of  the  body  built  ?  Name  some  of  the  different  kinds 
of  cells  and  tissues  in  the  body. 

What  do  the  cells  of  the  body  need  in  order  that  they  may 
live?  What  is  meant  by  health?  by  sickness?  What  fills  the 
crevices  among  the  cells?  What  is  lymph?  What  kind  of 
lymph  is  necessary  to  keep  the  cells  in  health?  What  organs 
prepare  food  for  the  cells?  What  organs  take  in  oxygen? 
What  organs  give  off  wastes  ?  What  happens  if  any  of  these 
organs  fail  in  their  work  ? 

SUGGESTIONS   TO   THE  TEACHER 

If  possible,  secure  a  compound  microscope  and  allow  the  pupils  to 
examine  cells.  Cells  scraped  from  the  inside  of  the  cheek  or  lip, 
or  the  living  skin  from  an  inner  layer  of  an  onion,  may  be  used  in 
demonstrating  cell  structure.  Prepared  longitudinal  sections  of  a 
growing  root  or  stem  tip  show  not  only  the  cells,  but  their  differentia- 


THE  HUMAN  BODY  AND  ITS  CELLS  15 

tion  into  tissues.  Make  clear  the  point  that  bone,  cartilage,  and 
connective  tissue  are  built  by  the  cell  depositing  dead  materials  about 
themselves,  and  that  the  living  cells  constitute  only  a  small  part  of 
these  supporting  tissues. 

Identify  parts  in  a  simple  flower;  demonstrate  pollen  under  a 
microscope.  The  pollen  grains  may  be  made  to  germinate  by 
placing  them  in  a  solution  of  sugar  and  water  (a  5  per  cent  to  40 
per  cent  solution,  according  to  the  kind  of  pollen  used).  Have  the 
pupils  plant  sunflower  seeds  in  pots.  Select  two  equally  vigorous 
plants ;  give  one  plenty  of  light  and  water,  and  set  the  other  in  a 
dark  corner  of  the  room  and  allow  the  soil  to  become  dry.  Note 
the  difference  in  the  appearance  of  the  plants  and  call  attention  to  the 
fact  that  the  human  body,  like  plants,  is  dependent  on  environment. 

Statistics  show  that  for  each  death  in  a  community  there  are  on 
an  average  about  two  years  of  sickness.  From  local  vital  statistics 
have  the  pupils  compute  how  many  years  of  sickness  are  annually  ex- 
perienced by  the  people  of  your  city  and  state. 

The  economic  loss  from  preventable  disease  is  estimated  at  $16 
per  year  for  each  inhabitant  of  the  United  States ;  compute  the 
yearly  loss  to  your  city  and  state  from  this  cause.  Borrow  compound 
interest  tables  from  a  bank  and  have  members  of  the  class  find  what 
sum  the  average  American  citizen  would  have  to  his  credit  at  20  and 
60  years  of  age  if  this  waste  could  be  stopped  and  the  money  in- 
vested at  5  per  cent  compound  interest. 


CHAPTER    THREE 


THE  FRAMEWORK   OF   THE   BODY 

ANY  one  looking  at  the  solid  walls  of  a  tall  building 
would  naturally  suppose  that  these  walls  carried  the 
weight  of  the  great  structure  above  them.  As  a  matter 
of  fact,  the  building  has  a  steel  framework  which  sup- 
ports it  and  braces  it  in  time  of  storm, 
and  the  walls  do  not  bear  even  their 
own  weight.  This  is  shown  by  the 
fact  that  the  workmen  often  finish 
a  portion  of  the  wall  many  stories 
above  the  ground,  before  they  build 
in  the  parts  that  connect  it  with  the 
earth.  The  important  thing  in  sup- 
porting the  building,  therefore,  is 
the  hidden  framework  which  out- 
lines the  shape  of  the  building  and 
carries  its  weight ;  it  is  not  the 
walls,  which  are  a  mere  covering 
hanging  on  the  framework. 

The  skeleton.     The  human  body, 

F,G.  =0.     The  weigh,  of     Hke  a  gr6at  Aiding.   haS    a   frai»e- 

the  building  is  carried  by    work  which  gives  the  body  its  shape 

the  steel  framework/  and    provideS    Support   for   it.       This 

framework  is  composed  of  206  bones.     All  the  bones 
taken  together  are  called  the  skeleton. 

In  addition  to  supporting  the  body,  the  bones  protect 
delicate  organs  like  the  brain  and  heart,  and  make  it 
possible  for  the  muscles  to  move  the  different  body 
parts.  Feel  your  wrists,  your  sides,  your  cheeks,  or 
almost  any  part  of  your  body,  and  you  will  find  the 
bones  under  the  skin  and  soft  flesh.  We  shall  now 

16 


THE  FRAMEWORK  OF  THE  BODY  IJ 


cranium 


skull 


clavicle 
sternum 

humerus 


spinal 
column 

pelvic  bone 

sacrum 

coccyx 


carpal  bones 
metacarpals 
phalanges 


tarsal  bones 

metatarsals 
^phalanges 


FIG.  21.    The  skeleton. 


1 8  PRIMER   OF  PHYSIOLOGY 

study  the  more  important  bones  of  the  skeleton  and 
the  way  in  which  these  bones  are  joined  to  make  a 
framework  for  the  body  as  a  whole. 

The  spinal  column  the  center 
of  the  skeleton.  The  backbone, 
or  spinal  column,  is  the  center 
around  which  the  whole  skeleton 
is  built.  Not  only  does  it  run  up 
the  back  and  stiffen  and  support 
the  trunk,  but  it  also  carries  the 
head  on  its  top,  and  it  has  the 
bones  of  the  chest  and  the  bones 
of  the  hips  attached  to  it.  It  is 
composed  of  many  short  bones,  — 
an  arrangement  which  gives  it  a 
great  number  of  joints  and  enables 
it  to  bend  freely  and  easily  in  any 
direction.  Each  bone  of  the 
spinal  column  is  called  a  vertebra 
(plural,  vertebra}.  Five  of  the 
lower  vertebrae  are  joined  to  make 
one  large,  solid  bone  which  is 
called  the  sacrum.  Below  the 
sacrum  there  are  three  or  four 
small  vertebrae  which  form  a  little 
tail-like  structure,  the  coccyx,  on 
the  end  of  the  spinal  column. 

FIG.  22.    The  skeleton  of  the          The  gkull        The  skeleton  of  the 
head  and  trunk. 

head,  or  skull,  is  composed  of  the 

fourteen  bones  of  the  face  and  of  eight  bones  which  make 
a  strong  box  (the  cranium)  to  protect  the  brain.  In  the 
skull  of  a  little  baby  there  are  places  where  the  bones 


THE  FRAMEWORK  OF  THE  BODY  19 

have  not  completely  covered  the  brain.  A  baby's  head, 
therefore,  needs  to  be  protected  carefully  from  blows. 

The  ribs  and  sternum.  The  ribs  are  twelve  pairs  of 
slender  bones  which  curve  around  the  chest  and  protect 
the  heart  and  lungs.  At  the  back  they  are  attached  to 
the  spinal  column.  In  front,  the  seven  upper  pairs  are 
joined  to  the  breast-bone,  or  sternum,  and  the  next  three 
pairs  are  hung  from  the  ribs  above.  The  two  lower  pairs 
have  their  front  ends  free,  and  are  called  floating  ribs. 

The  bones  of  the  shoulder.  The  shoulder  has  two 
bones,  —  the  collar-bone,  or  clavicle,  and  the  shoulder 
blade,  or  scapula.  The  scapula  is  a  flat  bone  which  lies 
oh  the  back  of  the  shoulder.  It  is  fastened  to  the  spinal 
column  and  ribs,  and  at  its  outer  end  has  a  socket  for 
the  head  of  the  arm  bone.  The  clavicle  has  its  inner 
end  attached  to  the  sternum ;  its  outer  end  is  propped 
against  the  point  of  the  scapula,  which  it  supports. 
When  the  clavicle  is  broken,  as  by  a  fall,  the  shoulder 
drops  forward  and  downward. 

The  pelvis.  The  pelvic  or  hip  bones  are  two  large, 
widespreading,  flat  bones  that  can  easily  be  felt  in  the 
sides.  They  are  firmly  joined  to  the  sacrum  at  the  back 
and  to  each  other  in  front.  With  the  sacrum,  these 
bones  form  the  bowl-shaped  pelvis,  which  gives  support 
to  the  organs  that  lie  in  the  lower  part  of  the  cavity  of 
the  abdomen  and  also  furnishes  a  solid  framework  to 
which  the  legs  are  attached. 

The  bones  of  the  limbs.  Each  limb  has  in  it  thirty 
bones,  and  the  bones  of  the  arm  and  leg  are  very 
similar.  The  thigh  has  in  it  a  great  bone  called  the 
femur,  and  the  arm  has  in  it  a  corresponding  bone  called 
the  humerus.  In  the  leg  below  the  knee  there  are  two 


20 


PRIMER   OF  PHYSIOLOGY 


FlG.  23.  From  an  X-ray 
photograph  of  a  broken 
forearm  and  a  wrist.  The 
crosses  show  where  the 
bones  are  broken. 


long  bones,  the  tibia  and  the  fibula,  and  in  the  forearm 
there  are  two  similar  bones,  the  ulna  and  the  radius. 
In  the  wrist  we  find  a  group  of  small 
bones  (the  carpal  bones),  and  in  the 
ankle  is  another  group  of  small  bones 
(the  tarsal  bones).  In  the  hand  are 
five  bones  (metacarpals\  each  bear- 
ing a  finger,  and  in  the  foot  are  five 
bones  (metatarsals),  each  bearing  a 
toe.  Finally,  the  fingers  of  each 
hand  have  in  them  fourteen  bones 
{phalanges),  and  the  toes  have  the 
same  number  of  bones  arranged  in 
the  same  way.  The  arms  and  legs 
are  built  on  the  same  general  plan, 
but  the  wrist  has  one  more  bone 
than  the  ankle,  and  the  elbow  has  no  bone  correspond- 
ing to  the  kneecap  (patella)  on  the  front  of  the  knee. 

Bones  composed  of  animal  and  mineral  matter.  A  bone 
is  composed  of  animal  matter  and  mineral  matter.  The 
mineral  matter  is  lime.  The  animal  matter  consists  chiefly 
of  tough  fibers  buried  in  the  mineral  groundwork  of  the 
bone.  The  animal  matter  gives  the  bone  its  toughness 
and  keeps  it  from  breaking.  The  mineral  matter  stiffens 
it  and  makes  it  able  to  bear  the  weight  of  the  body. 

These  statements  you  can  prove  for  yourself  by  burn- 
ing one  bone  in  the  fire  and  soaking  another  in  a  weak 
acid.  The  first  bone  has  the  animal  matter  burned 
out  of  it  and  becomes  brittle  like  chalk.  The  mineral 
matter  is  eaten  out  of  the  other  bone  by  the  acid,  and 
the  bone  becomes  limber  like  a  piece  of  rubber  tubing. 
You  can  easily  imagine  the  difficulties  you  would  be 


THE  FRAMEWORK   OF  THE  BODY 


21 


in  if   your  skeleton   lacked  either  the  mineral   matter 
which  stiffens  it  or  the  animal  matter  which  toughens  it. 

Joints.  Close  your  hand 
and  watch  your  fingers  as 
they  bend.  The  bending  is 
not  in  the  bones  themselves, 
but  at  the  joints  between  the 
bones,  and  the  advantage 
of  having  a  jointed  skeleton 
is  that  it  makes  movement 
possible.  There  are  two 
principal  kinds  of  joints  in 
the  body,  —  ball-and-socket 

;  .    .  FIGS.   24  and  25.     On  the  left  is 

joints  and  Ilinge  JOintS.        I  he    shown  the  shoulder  joint,  an  exam- 
former     allow    motion    freely    Ple  of  a  ball-and-socket  joint.    On 

the  right  is  the  elbow  joint,  an  ex- 

m  any  direction;  the  latter  ample  of  a  hinge  joint, 
allow  motion  only  in  two  op- 
posite directions,  as  does  a  hinge.  Good  examples  of  ball- 
and-socket  joints  are  found  in  the  shoulder  and  the  hip  ;  of 
hinge  joints  at  the  elbow,  at  the  knee,  and  in  the  fingers. 
Cartilage  and  ligaments.  The 
ends  of  the  bones  at  the  joints  are 
covered  with  a  smooth,  white  material 
called  cartilage,  which  is  kept  moist 
by  an  oil  that  is  secreted  in  the 
joints.  This  keeps  down  friction 
in  the  joints.  Around  the  joints 
are  many  strong  bands  and  cords 
of  connective  tissue  called  liga- 
ments. Their  chief  function  is  to 
tie  the  bones  together,  but  they 
also  inclose  the  joints  so  that  the  oil  cannot  escape. 


FIG.  26.     The  ligaments 
of  the  wrist. 


22  PRIMER   OF  PHYSIOLOGY 

The  treatment  of  sprains.  When  a  joint  is  bent  too 
far,  the  ligaments  about  it  are  either  torn  loose  from  the 
bones  or  broken.  An  injury  of  this  kind  is  called  a 
sprain,  and  a  bad  sprain  is  often  more  serious  than  a 
broken  bone.  The  best  way  to  prevent  a  sprained 
joint  from  becoming  swollen  and  painful  is  to  bathe  it 
in  hot  water  and  to  massage  it,  rubbing  and  stroking  it 
in  the  right  direction  to  send  the  blood  and  lymph  back 
up  the  limb  to  the  heart.  Driving  the  lymph  on  in  this 
way  will  lessen  the  swelling ;  it  will  take  the  pressure 
off  the  nerve  endings  and  so  help  to  relieve  the  pain ;  it 
will  carry  away  the  parts  that  die  because  of  the  break- 
ing and  tearing  of  the  ligaments ;  and  the  fresh  blood 
and  lymph  will  bring  a  supply  of  oxygen  and  food  that 
will  hasten  the  building  up  of  new  ligaments. 

There  is  a  widespread  idea  that  a  sprained  joint  heals 
most  rapidly  when  it  is  given  complete  rest,  but  many 
who  are  skilled  in  treating  sprains  and  dislocations 
insist  that,  if  the  joint  can  be  properly  supported,  the 
injured  member  should  be  used  as  soon  as  possible, 
even  when  movement  causes  pain.  The  reason  given 
for  this  treatment  is  that  exercise  helps  to  keep  up  a 
good  circulation  through  the  part  and  also  lessens  the 
danger  of  the  new  ligaments  being  formed  so  short 
that  the  joint  will  be  left  stiff  after  the  injured  tissues 
have  healed. 

Dislocations.  When  a  bone  is  thrown  out  of  place,  it 
is  said  to  be  dislocated.  A  few  persons  have  joints  so 
loosely  tied  together  that  a  dislocation  is  possible  with 
little  or  no  injury  to  the  ligaments,  but  usually  in  a  case 
of  dislocation  the  ligaments  are  badly  torn  and  broken. 
In  such  a  case,  no  one  but  a  physician  should  be  allowed 


THE  FRAMEWORK  OF  THE* BODY  23 

to  try  to  put  the  bones  back  in  place ;  for  an  unskilled 
person  may  cause  much  pain  and  do  great  damage  by 
pulling  and  twisting  at  an  injured  limb. 

Broken  bones.  When  an  arm  or  a  leg  is  broken,  it 
should  be  kept  stretched  out  straight  so  that  the  sharp, 
broken  ends  of  the  bone  will  not  cut  the  muscles,  nerves, 
and  blood  vessels 
of  the  limb.  If 
the  person  must 
be  moved,  wrap 
a  pillow,  coat,  or 
blanket  about  the 
injured  member, 

Vising;      Sticks     Or     FlG'  27'     A  broken  limb  bandaSed  for  moving  the 
°  patient. 

something      else 

stiff  enough  to  keep  it  from  bending,  as  shown  in  Figure 
27.  An  injured  person  may  be  carried  in  a  blanket,  but 
a  door,  a  cot,  or  other  solid  support  is  better.  In  lifting 
the  person,  take  the  greatest  .care  to  keep  the  injured 
limb  from  bending  sharply  at  the  break. 

The  two  parts  of  a  fractured  bone  are  cemented  sol- 
idly together  by  a  jelly-like  white  substance  which  ap- 
pears on  the  broken  ends  and  hardens.  If  the  broken 
ends  are  not  brought  together,  the  fracture  cannot  heal ; 
and  if  the  injured  part  is  not  properly  bandaged,  there 
is  always  great  danger  that  the  bone  will  be  crooked  or 
deformed  after  it  has  healed. 

The  skeletons  of  old  persons  and  of  children.  The 
bones  of  old  persons  have  very  little  of  the  living  animal 
matter  in  them.  They  therefore  break  easily,  and  be- 
cause they  contain  little  living  matter,  a  fracture  in  an 
old  person  heals  very  slowly  or  refuses  to  heal  at  all. 


24  PRIMER   OF  PHYSIOLOGY 

Old  persons,  therefore,  should  be  saved  as  much  as  pos- 
sible from  climbing  stairs  and  from  doing  other  things 
that  may  cause  them  to  fall. 

In  little  children,  on  the  other  hand,  there  is  a  small 
quantity  of  the  mineral  matter  in  the  skeleton,  and  the 
bones  can  easily  be  bent  into  almost  any  shape.  During 
the  growing  years,  large  amounts  of  lime  are  needed  for 
building  and  hardening  the  skeleton,  and  in  most  cases  of 
defects  and  deformities  of  the  skeleton,  the  real  trouble 
is  caused  by  a  lack  of  proper  building  materials  or  of 
other  necessary  substances  in  the  food  (pages  140,  141). 

Importance  of  caring  for  the  skeleton  in  youth.  Heavy 
lifting  will  cause  the  shoulders  of  a  child  to  droop  for- 
ward, making  him  round-shouldered ;  making  children 
sit  with  the  feet  hanging  over  the  edge  of  a  seat  will 
cause  the  legs  to  be  bowed;  tight  clothing  may  bend 
in  the  ribs  and  cramp  the  organs  within  the  body ; 
habitually  sitting  or  standing  in  a  stooped  position  will 
cause  the  skeleton  to  harden  in  an  incorrect  shape  ;  and 
many  persons  have  the  face  and  head  slightly  one-sided 
because  when  they  were  babies  they  were  allowed  to  lie 
on  one  side  more  than  on  the  other.  The  skeleton 
should  have  especial  care  in  youth;  for  after  the  bones 
have  hardened,  it  is  difficult  to  change  their  shape. 

QUESTIONS 

Give  three  functions  of  the  skeleton.  Of  how  many  bones 
is  the  skeleton  composed?  What  is  the  function  of  the  spinal 
column?  What  is  one  of  the  bones  of  the  spinal  column 
called?  What  is  the  sacrum,  and  of  what  is  it  composed?  the 
coccyx?  How  many  bones  are  in  the  skull?  What  is  the 
cranium  ?  Why  should  a  baby's  head  be  protected  from  blows  ? 


THE  FRAMEWORK  OF  THE  BODY  2$ 

How  many  ribs  are  there  in  the  body?  What  is  their  use? 
How  are  they  attached  at  the  back?  in  front?  Name  and  de- 
scribe the  two  bones  of  the  shoulder.  Describe  the  hip  bones. 
To  what  are  they  attached  at  the  back?  in  front?  How  many 
bones  are  there  in  each  limb?  Name  the  bones  of  the  arm. 
Name  the  bones  of  the  leg. 

Of  what  is  a  bone  composed  ?  What  is  the  use  of  the  animal 
matter?  of  the  mineral  matter?  How  can  this  be  proved? 

Name  the  two  principal  kinds  of  joints  in  the  skeleton. 
Explain  the  kinds  of  movements  they  allow  and  give  examples 
of  them.  What  is  cartilage?  How  is  friction  in  the  joints 
prevented?  Give  two  functions  of  ligaments. 

What  is  a  sprain  ?  What  treatment  should  be  given  a  sprain? 
Why?  Why  should  a  sprained  joint  be  exercised?  What  is  a 
dislocation  ?  Why  should  a  broken  arm  or  leg  be  kept  from 
bending?  How  can  this  be  done  while  moving  an  injured 
person?  How  does  a  broken  bone  heal?  Why  do  the  bones 
of  old  persons  break  easily  and  heal  with  difficulty?  Why  are 
the  bones  of  little  children  easily  bent?  What  mineral  should 
be  abundantly  supplied  in  the  diet  of  a  child?  Name  six 
things  that  may  cause  the  skeleton  of  a  child  to  take  an 
incorrect  shape. 

SUGGESTIONS    TO  THE  TEACHER 

Show  the  supporting  skeleton  of  a  leaf,  using  either  an  old  leaf 
from  which  the  softer  tissues  have  fallen  away,  or  one  that  has  been 
skeletonized  by  boiling  it  in  a  10  per  cent  potassium  hydroxid 
(KOH)  solution  and  gently  scraping  away  the  soft  tissues. 

Use  the  dry  bones  of  animals  in  teaching  the  skeleton  ;  decalcify 
the  drumstick  of  a  chicken,  or  any  other  slender  bone,  by  soaking  it 
in  water  to  which  acid  (hydrochloric,  sulfuric,  or  nitric)  has  been 
added.  Such  a  bone,  as  well  as  a  skeletonized  leaf,  may  be  preserved 
in  alcohol  or  in  a  50  per  cent  aqueous  solution  of  glycerin. 


CHAPTER   FOUR 

THE  MUSCLES  AND  THE  CARRIAGE  OF   THE  BODY 

IT  is  a  law  of  physics  that  a  body  at  rest  will  remain 
at  rest  forever,  unless  some  force  sets  it  in  motion  by 
pushing  or  pulling  on  it.  For  ex- 
ample, it  is  the  pulling  and  pushing 
of  the  hand  that  sends  a  thrown 
ball  upward  into  the  air.  It  is  the 
pull  of  the  earth  that  brings  the 
ball  down.  It  is  the  push  of  the 
gases  that  come  from  the  explosion 
of  the  powder  that  sends  the  pro- 
jectile from  a  great  gun.  It  is  the 
pressure  of  the  steam  in  the  cylin- 
ders of  an  engine  that  sets  the  ma- 
chinery in  motion  and  gives  it  the 
power  to  do  work.  Everywhere 
about  us  we  see  objects  set  in  mo- 
tion, and  in  every  case  this  is  done 
by  a  push  or  a  pull  from  an  outside 
source. 

You  can  lift  your  arms;  you  can 
extend  your   legs;  you   can   move 
your   whole    body    from    place   to 
place.     Something  must  be  push- 
ing or  pulling  the  different  parts 
of  the  body  to  cause  these  move- 
ments.    What  is  it  that  does  this 
FIG.  28.    The  muscles.     WOrk  ?     It  is  the  muscles  that  are 
stretched   upon  the    framework   of  the  body.      There 
are  more  than  five  hundred  of  these  muscles,  and  they 
make  up  two  fifths  of  the  body  weight.     You  are  famil- 

26 


MUSCLES  AND   THE  CARRIAGE  OF  THE  BODY     27 

iar  with  the  lean  meat  in  the  body  of  an  animal,  and  as 
this  is  muscle,  you  already  know  something  of  the  appear- 
ance and  texture  of  this  "  master  tissue  "  of  the  body. 

The  structure  of  a  muscle.  A  muscle  is  composed  of 
long,  slender,  fiber-like  cells,  which  have  the  power  of 
contracting,  or  shortening  and  thickening  themselves. 
This  action  of  the  muscle  fibers  may  be  illustrated  by 
allowing  a  stretched  rubber  band  to  come  back  to  its 
natural  condition;  or  you  can  get  an  idea  of  how  the 
muscle  cells  change  their  shape  by  watching  an  earth- 
worm shorten  and  thicken  its  body  as  it  crawls. 

The  long,  slender  cells  lie  lengthwise  in  a  muscle, 
and  among  them  is  a  great  network  of  connective  tissue 
fibers,  which  ties  the  whole  muscle  together  and  attaches 
it  to  the  skeleton.  When  the  muscle  fibers  contract,  they 
cause  the  whole  muscle  to  shorten  and  thicken,  as  you 
can  feel  by  laying  your  hand  on  your  upper  arm  while 
the  muscle  draws  itself  together  and  lifts  the  forearm. 

How  the  muscles  move  the  different  parts  of  the  body. 
The  muscles  stretch  across  the  joints  of  the  skeleton,, 
and  when  a  muscle  con- 
tracts, it  pulls  the  bones 
together  and  causes  a 
bending  at  the  joint. 
Exactly  how  this  is  done 
you  can  best  understand 
by  a  study  of  Figure  29. 

Tendons.     In    many 

parts     Of     the     body      long     FlcT^.     Showing  how  the  muscles  of 

cords  of  connective  tissue  the  arm  lift  the  forearm- 

called  tendons  attach  the  muscles  to  bones  that  are  at 
a  distance  from  them.  This  plan  of  placing  muscles 


28  PRIMER   OF  PHYSIOLOGY 

at  a  distance  from  the  parts  that  they  move,  keeps  mem- 
bers like  the  hand  from  being  covered  with  large  muscles, 
which  would  be  in  the  way  when  delicate  work  is  to  be 
done ;  at  the  same  time  it  gives  these  members  great 
strength  and  enables  them  to  make  many  different  move- 
ments. 

How  the  muscles  move  the  body  as  a  whole.     You  can- 
not stand  on  a  ladder  and  pull  the  ladder  up  after  you. 


muscle  . 

FIG.  30.    The  muscles  of  the  forearm  and  the  tendons  that  move  the  fingers. 

You  cannot  sit  on  a  chair  and  lift  it.  Yet  you  can  move 
your  whole  body  by  muscles  that  are  a  part  of  your 
body.  This  is  possible  because  you  have  a  jointed  skele- 
ton that  allows  you  to  thrust  out  parts  of  the  body  and 
push  against  outside  objects.  How  this  is  done  you  can 
test  understand  through  an  experiment.  Stand  close 
to  the  wall,  place  your  hands  against  the  wall,  and 
straighten  out  your  arms.  This  pushes  you  away  from 
the  wall  and  moves  your  whole  body. 

It  is  by  this  same  method  of  pushing  against  some- 
thing that  all  the  different  kinds  of  locomotion  in  the 
animal  kingdom  are  brought  about.  The  fish,  in  swim- 
ming, pushes  itself  forward  by  striking  its  tail  and  fins 
against  the  water.  The  bird,  in  flying,  forces  itself 
onward  and  upward  by  beating  against  the  air  with  its 


MUSCLES  AND   THE   CARRIAGE  OF  THE  BODY      29 

wings.     In  walking  and  running,   we  drive  ourselves 
forward  by  pushing  with  the  feet  against  the  ground. 

The  muscles  that  support  the  body.  Not  only  do  the 
muscles  move  the  body,  but  they  support  it  when  it  is 
held  erect.  Muscles  on  the  front  and 
the  back  of  the  neck  keep  the  head 
'balanced  on  top  of  the  spinal  column. 
When  we  stand  upright,  other  mus- 
cles hold  the  skeleton  from  bending 
at  the  ankles,  knees,  and  hips,  and  at 
the  joints  of  the  spinal  column.  The 
most  powerful  muscles  of  the  whole 
body  are  those  of  the  back,  which  lie 
both  in  front  of  the  spinal  column 
and  behind  it.  They  are  so  impor- 
tant in  the  carriage  of  the  body,  that 
we  shall  study  them  in  some  detail. 

Muscles  that  support  the  head.  The 
head  is  held  from  drooping  forward 
by  muscles  which  rise  from  the  verte- 
brae of  the  trunk,  from  the  ribs,  and 
from  the  bones  of  the  shoulder;  they 
are  attached  to  the  bones  of  the  neck 
and  to  the  back  of  the  skull.  The 
action  of  these  muscles  can  be  illus- 
trated by  attaching  a  string  to  the  first 
joint  of  the  finger,  as  is  shown  in 
Figure  32.  Other  muscles  on  the 

r  f   ^  ,       ,  ,  t  1  1      r  FlG-    31'      The 

front  of  the  neck  keep  the  head  from  that  lie  aiong  the  back 
being  drawn  too  far  backward.  of  the  spinal  column. 

The  muscles  that  support  the  trunk.     The  trunk  is 
kept   erect  by  muscles   along   the  back  of  the  spinal 


PRIMER    OF  PHYSIOLOGY 


column,  by  heavy  muscles  that  brace  the  spinal  column 
in  front  in  the  region  of  the  waist,  and  by  muscles  in 
the  walls  of  the  abdomen.  The  action  of  these  muscles 
we  shall  now  take  up  separately. 

The  muscles  along  the  back  of  the  spinal  column  rise 
from  the  sacrum  and  pelvic  bones  and  run  up  the  -back 
as  high  as  the  base  of  the  neck  (Fig.  31).  Their  func- 
tion is  to  keep  the  trunk  from  falling  forward.  Their 
action  may  be  illustrated  by  attach- 
ing a  cord  to  the  finger  and  drawing 
it  down  the  back  of  the  hand,  as  is 
shown  in  Figure  32. 

The  abdominal  muscles  are 
stretched  between  the  pelvic  bones 
and  the  ribs  and  sternum.  When 
they  contract,  they  draw  the  trunk 
forward  and  cause  it  to  stoop,  and 
they  keep  the  body  from  being 
drawn  over  backward  by  the 
muscles  of  the  back.  By  examin- 
/  ing  Figures  21  and  22,  you  will 

FIG.  32.     illustrating    the  see    how   these   muscles   are    at- 

attachment  and  action  of  the 

muscles  that  support  the  tached  and  you  Will  readily  Under- 
head  and  trunk,  stand  how  they  work  in  opposi- 
tion to  the  muscles  of  the  back. 

The  pull  of  the  muscles  along  the  back  causes  a 
forward  curve  in  the  spinal  column  at  the  waist.  The 
spinal  column  is  therefore  supported  in  front  in  this 
region  by  strong  muscles  that  brace  it  against  the  back 
muscles  and  keep  it  from  bending  too  far  forward.  The 
lower  ends  of  these  muscles  are  attached  to  the  femurs, 
which  they  lift  in  walking  and  running  (Fig.  33). 


MUSCLES  AND  THE  CARRIAGE  OF  THE  BODY     31 

The  body  balanced  over  the  feet  in  standing.  If,  in  stand- 
ing or  walking,  part  of  the  body  is  too  far  forward  or  back- 
ward, some  other  part  must  be  thrust  out  in  the  opposite 
direction  to  keep  the  balance  over  the  feet.  If  the  head 
droops  forward,  the  spinal  column  between  the  shoulders 
will  sink  backward  in  a  balancing  curve.  The  same  effect 
is  produced  by  the  shoulders  fall- 
ing forward  so  that  the  weight  of 
the  arms  pulls  forward  instead  of 
downward  at  the  sides.  If  the  back 
bends  inward  at  the  waist,  thrust- 
ing the  abdomen  forward,  the  up- 
per part  of  the  body  will  be  bent 
backward,  throwing  the  chest  up 
in  front.  Each  part  must  be  held 
in  correct  position,  for  one  part  out 
of  position  is  sure  to  force  other 
parts  out  of  position  also.  The 
following  rules  may  be  helpful  in 
keeping  the  body  in  correct  posi-  % 
tion  in  standing  and  walking  : 

"  Stand  tali;'  thrusting  up  the 
top  of  the  head  as  high  as  possible. 

Walk  as  if  you  were  hung  by 
the  top  ofyozir  head.  FlG-   33'    View    from    the 

front  of  one  of  the  muscles 

Hold  the  Chin  close  to  the  neck.       that  keep  the  spinal  column 
Press  the  back  of  the  neck  against    from  bending  too  far  forward 
.j          j,        j  at  the  waist. 

the  collar  button. 

Keep  tJie  abdomen  in. 

If  the  upper  part  of  the  body  leans  too  far  backward, 
so  that  the  heels  pound  in  walking,  sway  the  body  for- 
ward at  the  ankles  zintil  the  chest  is  over  the  toes. 


PRIMER   OF  PHYSIOLOGY 


In  walking  turn  the  toes  in. 

Health  and  vigor  are  most  important  in  acquiring  a 
correct  carriage,  for  if  the  muscles  that  hold  the  body 
upright  lie  weak  and  slack  on  the  skeleton,  they  must 
all  the  time  be  forced  to  do  the  work  that  they  ought  to 
do  naturally  and  without  effort. 

Mistakes  made  in  trying  to  secure  an  erect  carriage. 
When  the  head  droops  forward, 
the  mistake  is  often  made  of 
trying  to  bring  it  to  an  upright 
position  by  pulling  the  shoulders 
back.  The  true  remedy  is  to 
tighten  the  muscles  along  the 
back  of  the  neck  and  bring  to 
an  upright  position  the  upper 
part  of  the  spinal  column,  on 
which  the  head  rests. 

Another  mistake  commonly 
made  is  to  throw  the  head  and 
chest  back,  and  at  the  same  time 
allow  the  back  to  be  bent  in 
at  the  waist  and  the  abdomen 
FIG.  34.  The  vertical  line  pos-  to  be  thrust  forward.  In  this 
turetest.  (After  chart  supplied  case,  again,  the  remedy  is  to 

^courtesy  of  American  Posture     straighten  the  curye  in  the  spinal 

column.     The  muscles  that  lie 

along  the  front  of  the  spinal  column  in  the  abdominal 
region  are  attached  by  their  lower  ends  to  the  bones  of 
the  thighs,  and  one  of  the  exercises  that  is  practiced  in 
strengthening  them  is  to  lie  flat  on  the  back  and  draw 
the  legs  up  toward  the  body.  Walking,  running,  and 
hill  climbing  also  exercise  and  strengthen  these  muscles. 


MUSCLES  AND  THE  CARRIAGE  OF  THE  BODY      33 


A  third  mistake  often  made  is  to  try  to  bring  the 
shoulders  back  by  throwing  the  entire  upper  part  of  the 
body  backward.  The  shoulders  should  be  drawn  back 
without  moving  any  other  part  of  the  body,  by  pulling 
the  scapulas  flat  down  on  the  back. 

The  vertical  line  test  of  posture.     One  test  of  posture 


FIGS.  35,  36,  37.  The  figure  in  the  center  shows  correct  posture ;  the  head, 
neck,  and  trunk  form  one  continuous  vertical  line.  On  the  left,  the  head  is  too 
far  forward,  which  causes  the  spinal  column  to  bend  backward  between  the 
shoulders  and  forward  at  the  waist.  On  the  right,  the  shoulders  have  been 
drawn  up,  the  back  bent  inward  at  the  waist,  and  the  whole  upper  part  of  the 
body  thrown  too  far  backward.  In  the  figures  on  the  left  and  right  the  head, 
neck,  and  trunk  form  a  zigzag  line.  (After  chart  supplied  by  courtesy  of  Ameri- 
can Posture  League.} 

that  is  in  use  in  many  schools  is  called  the  vertical  line 
test.  If  a  vertical  line  is  dropped  from  in  front  of  the 
ear  to  the  forward  part  of  the  foot,1  the  long  axis  of 

1  By  forward  part  of  the  foot  is  meant  any  point  from  the  ball  of  the 
foot  back  to  the  middle  of  the  arch.  The  place  where  the  line  falls  on 
the  foot  varies  somewhat  in  different  persons. 


34 


PRIMER   OF  PHYSIOLOGY 


the  head,  neck,  and  trunk  will,  in  correct  standing 
position,  be  parallel  to  it  (Fig.  34).  If  the  position  is 
incorrect,  the  line  through  the  axis  of  the  body  will  be 
zigzag  and  not  a  straight  vertical  line.  The  test  can  be 
made  by  holding  a  pole  in  the  upright  position,  as  is 
shown  in  Figure  34.  The  vertical  line  should  pass  just 
in  front  of  the  knee  and  in  front  of  the  shoulder. 

When  the  trunk,  head,  and  neck  are  held  upright,  a 
vertical  line  drawn  through  the  middle  of  the  tip  of  the 
shoulder  should  pass  through  the  ear  or  behind  the  ear. 
If  this  line  passes  in  front  of  the  ear,  the  shoulder  is  too 
far  forward. 

The  foot  and  the  carriage  of  the  body.  Of  the  first 
million  drafted  men  who  appeared  at  our  army  canton- 
ments in  the  World  War,  more  than  175,000  had  flat 
feet,  and  in  1917  more  men  were 
discharged  from  the  service  for 
flat  feet  than  for  any  other  cause, 
except  pulmonary  tuberculosis. 
Since  deformed  or  painful  feet 
make  a  good  carriage  of  the  body 
impossible,  and  since  most  foot 
troubles  are  due  to  shoes,  we 
shall  take  up  in  this  chapter  the 
question  of  how  the  foot  carries 
the  body  weight,  and  of  fitting 
the  foot  with  a  correctly  shaped 
shoe. 

The  structure  of  the  foot.  The 
skeleton  of  the  foot  is  composed 
of  26  bones  which  are  held  to- 
gether by  muscles  and  ligaments. 


FIG.  38.  The  United  States 
Army  shoe.  Improper  shoes 
cause  so  much  foot  trouble 
that  one  United  States  Army 
surgeon  has  suggested  that  as 
a  measure  of  military  pre- 
paredness all  shoes  should  be 
manufactured  over  lasts  ap- 
proved by  the  government. 
It  is  especially  important 
that  the  feet  of  children  be 
not  deformed. 


MUSCLES  AND   THE  CARRIAGE  OF  THE  BODY      35 


FIGS.  39,  40,  and  41.  From  X-ray  photographs  taken  during  investigations 
made  by  the  United  States  Army.  Figure  39  shows  a  foot  in  a  shoe  supposed  to 
follow  the  lines  of  the  foot,  and  commonly  regarded  as  sensible.  Note  how 
the  bones  of  the  third  and  fourth  toes  are  curled  under,  and  how  the  great  toe 
is  bent  in  toward  the  other  toes.  Figure  40  shows  the  unshod  foot  of  a  soldier 
standing  on  one  leg  and  bearing  his  4o-pound  marching  equipment.  Note 
how  the  foot  expands  and  lengthens  under  pressure.  Figure  41  shows  a  foot 
in  the  United  States  Army  shoe  (Fig.  38).  Note  the  free  play  of  the  toes. 


Lengthwise  from  the  heel  to  the  ball  of  the  foot,  the 
bones  are  built  together  in  the  form  of  an  arch.  There 
is  also  a  cross  arch  in  the  foot  behind  the  toes,  similar 
to  the  arch  in  the  knuckles  of  a  closed  hand.  In  walk- 
ing, the  foot  is  moved  through  tendons  that  run  down 
along  the  ankle  from  the  muscles  below  the  knee  and 
are  attached  to  the  bones  of  the  foot.  The  foot  is  also 
to  a  considerable  extent  supported  and  held  from  tipping 
over  sidewise  by  the  pull  of  these  tendons  from  the  mus- 
cles of  the  leg. 

Shoes  that  interfere  with  the  work  of  the  foot.  The 
weight  of  the  foot  falls  on  the  heel,  on  the  great  toe 
and  the  ball  of  the  foot  behind  the  great  toe,  and  along 
the  outside  of  the  foot  behind  the  little  toe.  The  foot 
is,  therefore,  a  tripod,  and  if  anything  interferes  with 


PRIMER   OF  PHYSIOLOGY 


any  one  of  its  three  points  of    support,  it  becomes 
very  unsteady. 


FIGS.  42  and  43.    Showing  the  arch  of  the  foot,  and  how  a  high-heeled  shoe 
props  it  up  on  end. 

A  high-heeled  shoe  props  the  arch  of  the  foot  up  on 
end,  instead  of  allowing  it  to  stand  in  its  natural  position. 
Shoes  with  heels  that  slant  forward  move  the  back 
point  of  support  from  the  heel  toward  the  middle  of 
the  foot  and  make  walking  very  insecure  and  difficult. 
Shoes  with  pointed  toes  bend  the  great  toe  outward  and 
interfere  with  the  inner  front  point  of  support,  causing 
the  wearer  to  turn  the  toes  out  and  tending  to  cause  the 
arch  of  the  foot  to  be  turned  over  on  its  inner  edge.1 
Tight  shoes  interfere  with  the  outer  point  of  support  of 
the  foot  by  keeping  the  bones  back  of  the  toes  from 
springing  down  and  spreading  apart  in  a  natural  mariner 
and  thus  throwing  part  of  the  weight  on  the  outside  of 
the  foot.  All  this  causes  tired  and  painful  feet,  and 
makes  walking  difficult  and  fatiguing. 

1  In  the  heel,  the  point  of  support  is  toward  the  outside,  and  the  inner 
side  of  the  ankle  is  in  a  great  measure  held  up  by  tendons  from  the  muscles 
in  the  calf  of  the  leg.  If  for  any  reason  the  muscles  of  the  leg  are  weak, 
the  inner  side  of  the  ankle  is  not  sufficiently  supported  by  them  and  the 
arch  of  the  foot  is  allowed  to  turn  over  on  the  inside.  A  wide,  low  heel 
built  forward  and  out  under  the  inner  side  of  the  ankle  supports  the  foot 
at  this  weak  point. 


MUSCLES  AND  THE  CARRIAGE  OF  THE  BODY      37 

The  points  of  a  good  shoe.  A  good  shoe  should  have 
a  wide,  low  heel,  or  for  a  natural  foot,  no  heel  at  all.  It 
should  be  straight  along  the  inside  so  that  it  will  not 
bend  the  great  toe  around  toward  the  other  toes.  It 
should  be  long  enough  not  to  cramp  the  toes,  and  it 
should  have  a  box  in  it  high  enough  not  to  press  on  the 
toes  and  cause  corns  and  ingrowing  nails.  The  sole 
should  be  flat  across,  only  slightly  turned  up  at  the  toe, 
and  wide  enough  that  the  outer  border  of  the  foot  will 
not  overhang  it. 

It  is  especially  important  that  shoes  be  roomy  enough 
to  permit  the  feet  to  spread  and  the  toes  to  move  in 
walking ;  for  if  these  movements  are  not  allowed,  the 
muscles  of  the  feet  will  not  develop  and  will  lack  the 
strength  necessary  to  support  the  arches  under  the  body 
weight. 

The  position  of  the  foot  in  standing  and  walking.  In 
walking,  the  feet  should  be  carried  pointing  straight  for- 
ward ;  for  when  the  toes  are  turned  outward,  there  is  a 
tendency  for  the  arch  of  the  foot  to  be  turned  over  so 
that  it  lies  on  its  inner  side.  In  standing,  the  toes  may 
be  turned  outward  somewhat,  but  only  to  a  moderate 
degree.  A  person  who  "  toes  out "  should  practice  turn- 
ing his  toes  inward  as  he  walks.  This  position  of  the 
foot  is  very  important  in  securing  a  correct  carriage  of 
the  body. 

QUESTIONS 

How  many  muscles  are  there  in  the  body  ?  What  part  of 
the  body  weight  is  muscle  ? 

Describe  the  cells  of  a  muscle.  What  is  the  function  of 
the  connective  tissue  in  a  muscle  ?  How  does  a  muscle  cause 
the  skeleton  to  bend  at  a  joint  ?  What  is  a  tendon  ?  Of  what 


38  PRIMER  OF  PHYSIOLOGY 

advantage  is  it  to  have  tendons  in  the  body  ?  Explain  how 
the  muscles  move  the  body  in  walking  and  in  running. 

What  function  have  the  muscles  in  addition  to  that  of  mov- 
ing the  body?  What  muscles  support  the  head?  Describe 
the  three  sets  of  muscles  that  support  the  trunk. 

What  happens  if  in  standing  or  walking  any  part  of  the 
body  is  too  far  backward  or  forward  ?  Give  seven  rules  that 
may  help  in  securing  a  good  carriage  of  the  body.  Why  is 
health  important  in  securing  a  good  carriage  ?  Explain  three 
mistakes  that  are  commonly  made  in  trying  to  hold  the  body 
erect.  Explain  how  exercising  the  legs  keeps  the  spinal 
column  from  bending  too  far  forward  at  the  waist.  Explain 
the  vertical  line  test  of  posture.  Is  your  own  posture  correct 
by  this  test?  What  test  shows  when  the  shoulders  are  in 
correct  position  ?  How  may  they  be  pulled  backward  and 
what  mistake  should  be  avoided  in  attempting 'to  do  this  ? 

How  common  were  foot  troubles  among  the  drafted  men 
during  the  recent  war  ?  How  many  bones  are  there  in  the 
foot?  How  are  the  bones  held  together?  Where  are  the 
arches  in  the  foot  ?  Where  are  the  muscles  that  move  the  feet 
in  walking? 

Why  are  high-heeled  shoes  objectionable  ?  On  what  three 
points  of  the  foot  does  the  body  weight  fall  ?  What  is  the 
objection  to  narrow  heels  ?  to  heels  that  point  forward  ?  to 
shoes  with  pointed  toes  ?  to  tight  shoes  ?  Describe  a  good 
shoe.  What  is  the  correct  position  for  the  foot  in  standing  ? 
in  walking? 

SUGGESTIONS  TO  THE  TEACHER 

Bancroft's  The  Posture  of  School  Children  (Macmillan)  will  be 
most  helpful  to  the  teacher.  The  American  Posture  League,  No.  I 
Madison  Avenue,  New  York  City,  issues  charts  and  literature  on 
posture  and  gives  the  address  of  manufacturers  of  clothing,  shoes, 
.furniture,  and  other  articles  that  have  been  designed  to  meet  the 
standards  approved  by  the  League. 


CHAPTER    FIVE 


THE  HEART  AND  THE  CIRCULATION  OF  THE  BLOOD 

IN  New  York  City  the  street  cars,  automobiles,  and 
wagons  fill  the  streets ;  the  elevated  trains  roar  over- 
head ;  and  deep  in  the  earth 
the  trains  in  the  subway  rush 
on  and  on  in  a  procession 
that  never  ends.  Nor  is  this 
all  of  the  transportation  sys- 
tem of  the  city  ;  for  water  and 
gas  are  piped  underneath  the 
streets  to  the  homes  of  the 
people ;  most  of  the  wastes 
of  the  city  are  carried  away 
by  underground  sewer  pipes  ; 
and  the  electricity  which 
lights  the  city  and  runs  much 


Transportation   in   New 
York  City. 


of  its  machinery   passes  FlG-  44 

silently    along   wires   to   the 

places  of  its  use.     In  these  and  in  many  other  ways  the 

carrying  problem  of  the  city  is  solved. 

The  carrying  problem  in  the  body.  As  a  city  is  com- 
posed of  a  multitude  of  people,  so  is  the  body  composed 
of  a  multitude  of  cells  —  4OO,cx)O,ooo,ooo,  according  to 
one  estimate.  Each  of  these  cells  must  have  food  and 
oxygen,  and  each  must  get  rid  of  its  wastes.  There 
must,  therefore,  be  a  transportation  system  in  the  body, 
and  it  must  be  one  that  is  always  in  working  order  — 
not  one  that  breaks  down  and  fails  in  its  work  from  time 
to  time.  Transportation  by  water  is  more  reliable  than 
any  other  method  that  has  yet  been  devised,  and  this  is 
the  method  we  find  used  in  the  body. 

39 


40  PRIMER   OF  PHYSIOLOGY 

The  carrying  in  the  body  done  by  the  blood.  All 
through  the  body  there  is  a  great  system  of  tubes,  or 
pipes,  called  blood  vessels.  Night  and  day  the  heart 
pumps  the  blood  through  these  vessels.  Everything 
that  the  cells  need  is  dissolved  in  the  blood  and  carried 
to  them  in  the  blood  stream.  Into  this  stream  each  cell 
gives  off  its  wastes  to  be  carried  away.  Thus  all  the 
carrying  within  the  body  is  done  by  the  blood,  and  the 
blood  is  kept  in  constant  motion  through  the  body  by  the 
heart. 

Arteries  and  veins.  The  blood  in  its  movement,  or 
circulation,  through  the  body  flows  through  the  same 
channels  again  and  again,  always  returning  to  the 
starting  point,  the  heart.  We  have,  therefore,  two  sets 
of  blood  vessels  in  the  body, — the  arteries,  which  carry 
the  blood  from  the  heart,  and  the  veins,  which  bring  the 
blood  to  the  heart.  The  large  arteries  which  leave 
the  heart  send  branches  to  the  different 'parts. of  the 
body.  These  branches  divide  into  finer  and  finer 
branches,  called  capillaries,  which  run  in  among  all  the 
cells.  Then  the  capillaries  unite  into  small  veins.  The 
veins,  like  the  creeks  that  form  a  river,  keep  coming 
together,  until  finally  all  of  them  are  united  into  the 
great  veins  which  carry  the  bkfod  back  to  the  heart. 

To  understand  how  the  blood  passes  from  an  artery 
into  a  vein,  think  of  two  trees  standing  with  their  trunks 
close  together  and  their  tops  touching  each  other.  Then 
imagine  that  the  blood  flows  up  the  trunk  of  one  tree, 
out  into  its  branches  and  twigs,  then  on  into  the  twigs 
and  branches  of  the  other  tree,  and  down  its  trunk.  If 
the  blood  should  make  a  circuit  of  this  kind  through  the 
trees,  its  journey  would  be  like  the  one  that  it  makes 


THE  HEART  AND   THE  CIRCULATION 


liver 


left  auricle 
valves 

lung 
left 
ventricle 


intestine 
artery  to  leg 


FIG.  45.  Diagram  showing  the  circulation  of  the  blood.  Note  the  valves  be- 
tween the  auricles  and  ventricles  and  at  the  mouths  of  the  great  arteries  that 
open  out  of  the  ventricles. 


42 


PRIMER   OF  PHYSIOLOGY 


when  it  passes  out  from  the  heart  through  an  artery 

and  returns  to  the  heart  through  a  vein. 

The   heart.     The   heart   lies    in    the   chest   with   its 

point  to  the  left  of  the  center.  Its  walls  are  made  of 
strong  muscles,  and  within  the 
heart  are  four  chambers,  or  cavi- 
ties, two  on  each  side.  The  two 
upper  cavities  are  called  auricles  ; 
the  two  lower  cavities  are  called 
ventricles. 

The  action  of  the  heart.  The 
veins  pour  the  blood  into  the  auri- 
cles. Then  the  walls  of  the  auri- 
cles contract  and  force  the  blood 
down  into  the  ventricles.  Next, 
the  strong  walls  of  the  ventricles 
close  in  on  the  blood,  and  drive 
it  out  into  the  arteries  and  all 
through  the  body.  After  forcing 

FIG.  46.     The  heart.  11,1-  .  •  i 

the   blood    into   th9    arteries,    the 

walls  of  the  ventricles  relax,  and  for  a  moment  the  heart 
rests.  Then  again  the  auricles,  contracting  on  the  blood 
that  has  flowed  in  from  the  veins,  .fill 'the  ventricles, 
and  the  ventricles  pump  t'he  blood  on  into  the  arteries. 
Place  your  hand  on  the  left  side  of -your  chest,  and  you 
will  feel  your  heart  move  as  its  walls /close  in  on  the 
blood  and  force  it  onward  through  the  vessels. 

The  valves  of  the  heart.  In  every  pump  there  must 
be  valves  to  keep  the  liquid  from  flowing  backward. 
The  heart,  like  other  pumps,  is  provided  with  these 
valve's;'— 1; two7  between  the  ^auricles  arid%trYev  Vebtflcles, 
and  two  at  the 'mouths  of  tne  arteries  to  kee,p  the  blood 


THE  HEART  AND   THE  CIRCULATION"  43 


from  flowing  backward  into  the  ventricles  when  their 
walls  relax  and  the  chambers  open  after  each  beat.     In 


VALVE    CLOSED 


FlG.  47.  A  diagram  of  the  right  side  of  the  heart  showing  the  working  of 
the  valves.  When  the  blood  flows  into  the  auricles  and  the  ventricles  relax, 
the  valves  of  the  heart  are  as  shown  in  A.  When  the  ventricles  contract 
and  the  blood  flows  out  into  the  arteries,  the  valves  are  as  shown  in  B. 

Figure  45  you  can  study  out  where  the  valves  are 
placed,  and  from  Figure  47  you  can  understand  how 
they  prevent  a  backward  flow  of  the  blood 
in  the  vessels  and  in  the  heart. 

Tracing  the  circulation  of  the  blood. 
Trace  the  circulation  of  the  blood  in  Figure 
45,  and  you  will  see  that  the  heart  is  a 
double  organ  ;  that  the  right  side  sends  the 
blood  on  a  short  journey  through  the  lungs 
and  back  to  the  left  side ;  and  that  the  left 
side  drives  the  blood  into  the  arteries  for  a 
long  journey  through  all  the  body  and  back 
again  to  the  right  side  of  the  heart.  The 
blood  flows  through  the  vessels  very  swiftly, 
making  the  journey  through  the  lungs  in 
about  fifteen  seconds,  and  the  long  journey 
through  the  body  in  less  than  a  minute. 


FIG.  48.     A 

diagram  of  a 
pump.  Locate 
the  valves  and 
explain  how 
they  work. 


44 


PRIMER   OF  PHYSIOLOGY 


The  blood  composed  of  plasma  and  corpuscles.     The 

blood  is  composed  of  a  liquid  part  called  plasma,  and 
of  millions  of  little  cells  called  corpuscles,  which  float 
in  the  plasma.  About  nine  tenths  of  the  plasma  is 
water.  The  remainder  is  composed  of  dissolved  food 
and  other  materials  that  are  needed  by  the  cells,  and 
of  the  wastes  that  come  from  the  cells.  The  corpuscles 
are  of  two  kinds,  the  red  and  the  white.  The  red 
corpuscles  are  so  abundant  that  there  are  millions  of 
them  in  the  smallest  drop  of  blood. 
It  is  the  red  corpuscles  that  give  the 
red  color  to  the  blood. 

The  function  of  the  corpuscles.  As 
the  blood  passes  through  the  lungs, 
it  takes  oxygen  from  the  air  that  is 
breathed  into  the  lungs.  The  oxygen 
is  then  carried  through  all  the  body 
and  given  up  to  the  cells.  '  This  carry- 
ing of  the  oxygen  is  done  by  the  red 
corpuscles.  Like  little  boats  floating  in 
the  blood  stream,  they  take  up  their 
FIG.  49  Red  blood  loads  of  oxygen  m  the  lungs,  carry  the 

corpuscles     (A)     and  J& 

white  blood  corpuscles  oxygen  out  through  the  body,  unload 
^-  it  for  the  hungry  cells,  and  hasten  back 

to  the  lungs  for  more  of  the  oxygen  which  the  cells 
must  have.  The  importance  of  this  work  is  shown  by 
the  fact  that  when  the  heart  ceases  to  beat,  or  when 
a  person  is  under  water  so  that  the  oxygen  is  cut  off 
from  the  lungs,  the  life  of  the  body  quickly  comes  to 
an  end. 

The  white  corpuscles  are  larger  than  the  red  ones  and 
are  fewer  in  number.     Their  work  is  to  kill  the  disease 


THE  HEART  AND   THE  CIRCULATION 


45 


germs  that  get  into  the  body.     This  subject  we  shall 
discuss  in  a  later  chapter  (page  237). 

The  lymph.  The  blood  capillaries  are  so  small  and  so 
abundant  among  the  cells  that  you  cannot  stick  a  pin 
into  your  tissues  anywhere  without  breaking  many  of 
them  and  letting  the 
blood  escape.  The 
capillaries  have  very 
thin  walls,  and  as 
the  blood  flows 
through  them  some 
of  the  plasma  es- 
capes and  passes  out 
into  the  spaces 
among  the  cells. 
This  escaped  plasma 
is  the  lymph,  about 
which  you  have 
already  studied 
in  the  chapter  on 

the    Cells    (pages     12      is  plasma  that  escapes  through  the  thin  walls  of 
the  small  blood  vessels.     (Diagrammatic.) 

and  13). 

The  lymph  a  middleman  between  the  cells  and  the 
blood.  In  Figure  50  you  can  see  how  the  cells  lie 
among  the  capillaries,  and  how  they  are  bathed  in 
the  lymph  that  escapes  through  the  thin  walls  of 
these  vessels.  The  cells,  therefore,  are  not  in  the 
blood  stream,  but  this  stream,  so  to  speak,  merely 
passes  by  the  house,  and  the  cells  must  find  some 
way  of  getting  their  supplies  from  the  stream  into 
the  house.  This  is  done  through  the  lymph.  As 
the  red  corpuscles  pass  along  in  the  capillaries,  the 


lymph 


plasma 


while 
corpusde 

.red, 
corpusde 

FIG.  50.    The  cells  are  bathed  in  lymph,  which 


46  PRIMER   OF  PHYSIOLOGY 

oxygen  breaks  loose  from  the  corpuscles,  passes  out 
through  the  walls  of  the  vessels  into  the  lymph,  and 
so  reaches  the  cells.  In  the  same  way,  the  foods  that 
are  dissolved  in  the  plasma  make  their  way  out  into 
the  lymph  that  surrounds  the  cells,  and  the  wastes 
that  the  cells  give  off  pass  through  the  lymph  into 
the  blood  and  are  carried  away.  The  lymph  acts  as  a 
middleman  between  the  cells  and  the  blood,  passing  the 
oxygen  and  food  from  the  blood  to  the  cells,  and  the 
wastes  from  the  cells  to  the  blood. 

The  lymphatic  vessels.     Among  the  cells  of  the  body 
there  is,  besides  the  blood  capillaries,  a  system  of  fine, 

thin-walled  lymphatic  capilla- 
ries. These  unite  and  form 
larger  vessels,  which  finally 
empty  into  the  veins  of  the 
shoulders.  The  lymphatic 
vessels  act  as  a  drainage  sys- 


FIG.  51.      Lymphatic   vessels    in    tem  for    fa 

the  fingers.  -....-,  ,  , 

function  ts  to  gather  up  and 

drain  off  the  stale,  impure  lymph  from  among  the  cells 
and  empty  it  into  the  blood.  This  allows  fresh  lymph 
to  escape  .among  the  cells,  bringing  with  it  sup- 
plies of  food  and  oxygen.  The  lymphatic  vessels  of 
the  greater  part  of  the  body  unite  in  one  great  vessel 
called  the  thoracic  duct.  This  runs  up  the  back  of  the 
cavities  of  the  abdomen  and  chest,  and  empties  into  the 
large  vein  in  the  left  shoulder. 

The  importance  of  caring  for  the  heart.  The  respon- 
sibility of  keeping  the  whole  transportation  system  of 
the  body  in  operation  falls  on  the  heart,  which  is  usually 
about  the  size  of  the  fist  of  the  person  to  whom  it  be- 


THE  HEART  AND   THE  CIRCULATION          47 

longs.  Night  and  day,  from  birth  until  death,  this  little 
organ  pumps  away,  giving  a  stroke  oftener  than  once  a 
second.  We  cannot  replace  an  injured  valve  in  it  with  a 
new  one ;  it  could  not  stop  long  enough  for  that,  even 
if  we  knew  how  to  do  it.  If  it  be- 
comes overworked,  or  if  it  is  poisoned 
by  disease  germs,  there  is  no  second 
pump  to  take  its  place  while  it  rests 
and  gets  into  good  condition  again. 
It  is  such  a  wonderful  organ  that  usu-  FIG.  52.  Valves  in  an 
ally  it  gives  us  little  cause  for  com-  ^\^K^^ 
plaint;  yet  there  are  certain  things  three  valves  attached 
that  injure  the  heart,  and  for  our  own  h'ke  ^pockets  to 

J  the  wall  of  the  artery. 

good  We  OUght  to  know  of  these  things    When  the  blood  starts 

and  avoid  them.     We  shall  therefore   to  flow  backward  into 

.  .  the  heart,  it  catches  in 

mention  at  this  time  some  of  the  points  the  pockets,  which  then 
that  are  important  in  the  care  of  the   swing  out  and  close  the 

opening  into  the  heart. 

heart. 

The  heart  injured  by  disease  germs.  By  far  the 
most  common  cause  of  trouble  in  the  heart  is  disease 
germs.  In  diphtheria  and  scarlet  fever  the  nerves  and 
the  muscle  cells  of  the  heart  are  so  damaged  by 
the  poisons  produced  by  the  germs,  that  even  in  the 
mildest  cases  of  these  diseases,  physicians  frequently 
forbid  the  patient  to  sit  up  in  bed,  because  they  fear 
the  effect  of  the  strain  on  the  heart.  Furthermore,  the 
heart  is  often  so  poisoned  by  an  attack  of  one  of  these 
diseases  that  the  nerves  and  muscle  cells  never  recover, 
and  the  heart  is  left  weak  for  life.  In  other  diseases, 
such  as  pneumonia,  rheumatism,  and  influenza,  the  germs 
themselves  attack  the  valves  and  cause  them  to  shrivel 
and  harden,  so  that  they  allow  the  blood  to  leak  back- 


48 


PRIMER   OF  PHYSIOLOGY 


ward,  and  again  the  heart  is  damaged  for  life.  As 
much  as  possible,  therefore,  we  ought  to  avoid  all  these 
germ  diseases,  —  the  catching  diseases  which  are  so  com- 
mon, and  which  people  often  carelessly  give  to  each 
other.  After  an  attack  of  one  of  these  dis- 
eases, hard  exercise  should  be  avoided  until 
the  heart  has  had  time  to  regain  its  strength. 
Too  much  exercise  injurious  to  the  heart. 
When  the  muscles  are  working,  they  need 
more  food  and  oxygen  and  give  off  more 
FIG.  53.  A  wastes  than  when  they  are  at  rest.  The 


valve  in  a  heart  must  therefore  pump  the  blood  more 
veins  have  swiftly  through  the  body  when  we  use  the 
muscles. 


This  you  can  prove  for  yourself 


ward  when 
pres  sure 


valves  in  them 
to  prevent  the 

blood  from  by  noting  how  much  harder  and  faster  your 
flowing  back-  heart  beats  after  running  or  after  doing  other 
hard  work.  Indeed,  when  we  take  hard  and 
comes  on  the  long-continued  exercise,  it  is  -usually  the 
your5  finger  heart  that  becomes  tired  first  of  all,  although 
down  a  vein  we  may  not  feel  it. 

There  is  danger,  therefore,  of  overworking 
the  heart,  especially  at  that  time  of  life  when 
the  boy  or  girl  is  entering  manhood  or 


on  your  fore- 
arm, and  little 
knots  will 
stand  out  on 
the  vein  at  the 


points  where    womanhood  and  the  body  rapidly  increases 


"* 


in  size.  When  overworked,  the  heart,  like 
any  other  muscle,  at  first  enlarges,  and 
then,  if  the  overworking  is  kept  up,  becomes  weak  and 
flabby.  This  condition  of  the  heart  is  called  "athletic 
heart."  If  a  person  whose  heart  has  been  injured  by 
overexercise  takes  a  long  rest,  going  to  bed,  if  neces- 
sary, his  heart  usually  recovers.  He  ought,  however, 
to  take  care  not  to  force  his  heart  into  this  condition. 


THE  HEART  AND  THE  CIRCULATION          49 

Proper  and  improper  exercise.  Do  not  keep  on  at 
any  heavy  work  or  hard  game  until  you  are  exhausted. 
Do  not  play  tennis  all  day.  Do  not  spend  a  whole 
Saturday  afternoon  playing  football.  Remember  that 
a  baseball  pitcher  needs  a  stout  heart  as  well  as  a 
strong  arm,  and  that,  for  the  sake  of  both  your  arm 
and  your  heart,  you  should  not  stay  in  the  pitcher's  box 
a  whole  half-day  at  a  time.  Do  not  enter  long  Mara- 
thon races  that  are  intended  for  men  and  not  for  boys, 
and  do  not  get  on  your  bicycle  and  ride  at  a  fast  pace, 
hour  after  hour,  up  hill  and  down.  You  should  under- 
stand, however,  that  it  is  only  overwork  that  you  are 
being  cautioned  against,  and  that  both  moderate  exercise 
and  severe  exercise  taken  for  short  periods,  are  bene- 
ficial to  the  heart,  as  well  as  to  other  parts  of  the  body. 

Tobacco  injurious  to  the  heart.  Tobacco  sometimes 
damages  the  heart  until  it  has  a  quick,  weak,  and  flut- 
tery  beat.  This  is  a  serious  ailment,  but  usually,  if  the 
tobacco  is  given  up,  the  heart  seems  in  time  to  recover. 
Coaches  and  trainers  will  not  allow  athletes  to  smoke, 
because  smoking  weakens  both  the  heart  and  the  other 
muscles.  The  question  of  the  effects  of  tobacco  on  the 
body  we  shall  discuss  in  more  detail  in  a  later 
chapter  (page  197). 

The  heart  injured  by  headache  remedies.  A  number 
of  drugs  commonly  used  (among  them  phenacetin,  ace- 
tanilid,  and  antipyrin)  will  check  a  headache.  The  prac- 
tice of  taking  these  drugs  for  headaches  and  colds  is 
dangerous ;  for  they  all  weaken  the  action  of  the  heart, 
and  their  continued  use  will  bring  on  heart  disease. 
They  should  be  taken  only  when  prescribed  by  a  physi- 
cian, and  no  good  physician  will  prescribe  them  often 


50  PRIMER  OF  PHYSIOLOGY 

for  the  same  person;  for  treating  a  headache  in 
this  way  is  not  finding  and  removing  the  cause  of 
the  trouble,  but  drugging  the  body  so  that  the  pain 
will  not  be  felt. 

The  effects  of  alcohol  on  the  heart  and  blood  vessels. 
Alcohol  causes  the  walls  of  the  blood  vessels  to  become 
weak  and  brittle.  For  this  reason,  apoplexy,  which  is 
caused  by  the  bursting  of  a  blood  vessel  in  the  brain, 
is  more  common  among  users  of  alcohol  than  among 
abstainers.  Alcohol  often  weakens  the  heart  by  caus- 
ing its  muscle  cells  to  change  to  fat.  In  many  beer 
drinkers  there  is  the  additional  trouble  that  the  work- 
ing cells  of  the  heart  are  buried  in  a  great  mass  of  fat 
that  must  be  lifted  and  moved  every  time  the  heart 
beats.  When  one  realizes  that  in  germ  diseases  every- 
thing depends  on  the  heart's  keeping  at  work  until 
the  body  has  had  time  to  overcome  the  germs  that  are 
attacking  it,  the  disastrous  effects  of  alcohol  are  more 
easily  understood.  In  pneumonia,  especially,  when  it 
is  a  great  task  for  the  heart  to  drive  the  blood  through 
the  congested  lungs,  and  in  diseases  in  which  the 
heart  is  weakened  by  the  poisons  from  the  germs,  it 
is  most  important  that  the  full  power  of  this  organ  be 
saved  for  the  ordeal  which  it  must  undergo.  Statistics 
from  a  hospital  in  a  city  where  excessive  beer  drink- 
ing is  very  common,  show  that  1 6  per  cent  of  all  deaths 
in  the  hospital  were  due  to  "beer-drinker's  heart." 

Digestive  troubles  and  the  heart.  When  the  digestive 
organs  are  out  of  order,  the  stomach  sometimes  becomes 
filled  with  gas  and  presses  on  the  heart,  causing  a  most 
uncomfortable  feeling  and  a  pounding  and  irregular 
beating.  The  digestive  system,  of  course,  should  be 


THE  HEART  AND   THE  CIRCULATION-  51 

given  proper  treatment  in  cases  of  this  kind,  but  if  this 
is  done,  there  need  be  no  alarm  about  the  heart  itself. 


QUESTIONS 

What  must  be  carried  to  the  cells  and  away  from  them? 
How  is  this  carrying  done?  What  is  the  movement  of  the 
blood  through  the  body  called?  What  is  an  artery?  What  is 
a  vein?  What  is  a  capillary?  How  does  the  blood  pass  from 
an  artery  into  a  vein? 

Describe  the  heart.  Explain  how  the  heart  forces  the  blood 
through  the  body.  Where  are  the  valves  in  the  heart  and  what 
is  their  use?  Trace  the  circulation  of  the  blood  from  the  right 
auricle  back  again  to  the  right  auricle. 

Of  what  is  the  blood  composed?  Of  what  is  the  plasma 
composed?  What  is  the  function  of  the  red  corpuscles?  of 
the  white  corpuscles?  What  is  the  source  of  the  lymph?  Ex- 
plain how  the  lymph  acts  as  a  middleman  between  the  cells 
and  the  blood.  Describe  the  lymphatic  vessels.  What  is  their 
function  ?  What  and  where  is  the  thoracic  duct  ? 

Why  is  the  care  of  the  heart  so  important?  What  is  the 
most  common  cause  of  injury  to  the  heart?  How  does  over- 
exercise  affect  the  heart?  At  what  age  is  the  heart  especially 
likely  to  be  injured  by  overexercise  ?  Name  some  games  that 
put  a  great  strain  on  the  heart. 

What  effect  has  tobacco  on  the  heart?  Name  some  drugs 
that  are  commonly  used  as  headache  remedies.  What  effect 
have  these  drugs  on  the  heart?  How  do  they  relieve  a  head- 
ache? What  effect  has  alcohol  on  the  blood  vessels?  What 
causes  of  death  are  especially  common  among  drinkers  on 
account  of  this  effect  of  alcohol  on  the  vessels?  What  effect 
has  alcohol  on  the  heart?  When  is  the  bad  effect  of  alcohol 
on  the  heart  especially  likely  to  show  itself  ?  What  effect  does 
indigestion  sometimes  have  on  the  heart  ? 


52  PRIMER   OF  PHYSIOLOGY 


SUGGESTIONS  TO  THE  TEACHER 

If  possible,  secure  a  glass  model  of  a  pump,  such  as  is  commonly 
found  among  the  equipment  of  an  elementary  physical  laboratory, 
and  demonstrate  the  action  of  the  valves.  Allow  the  pupils  to  ex- 
amine a  drop  of  blood  under  the  microscope.  Additional  matter  on 
the  topics  discussed  in  this  chapter  and  in  many  of  the  other  chapters 
in  this  book  will  be  found  in  Human  Physiology,  the  most  advanced 
book  of  the  series. 

An  examination  of  the  diagram  on  page  234  will  show  that  heart 
disease  is  one  of  the  great  causes  of  death.  It  is  now  generally 
accepted  that  practically  all  cases  of  heart  disease  (as  well  as  cases 
of  rheumatism,  Bright's  disease,  and  disease  of  the  arteries)  are 
caused  by  germs.  Usually  these  germs  are  slow-growing  races  of 
streptococci,  and  often  they  have  a  permanent  breeding  ground  in 
the  tonsils,  at  the  roots  of  teeth,  in  the  bones  of  the  face,  or  in  some 
other  part  of  the  body,  and  are  carried  from  these  "  foci  of  infec- 
tion "  to  the  heart  and  other  organs.  In  overcoming  these  slow 
infections,  a  hygienic  life  is  of  great  importance,  but  treatment  of  the 
teeth  or  other  infected  part  is  often  necessary.  The  relation  of 
these  chronic  infections  to  the  general  health  should  be  brought  to 
the  attention  of  the  class  during  the  study  of  later  chapters. 


CHAPTER   SIX 


RESPIRATION 

FILL  a  bottle  with  boiled  water  and  one  with  unboiled 
water,  and  arrange  growing  beans  in  them,  as  is  shown 
in  Figure  54.  The  bean  with  its  roots 
in  unboiled  water  will  grow  for  a  consid- 
erable time  —  as  long  as  the  mineral  mat- 
ter in  the  water  will  provide  it  with  food 
materials.  The  roots  of  the  plant  in  the 
boiled  water  will  quickly  die  and  the 
whole  plant  will  then  wither,  because 
the  roots  no  longer  send  the  water  up  to 
the  leaves. 

Why  is  it  that  the  roots  in  the  boiled 
vvater  die  ?  The  answer  is  simple.  The 
boiling  of  the  water  drives  the  oxygen  out 
of  it,  and  without  oxygen  the  cells  of 
neither  plants  nor  animals  can  remain 
alive. 

The  object  of  respiration.  The  first  object  of  respiration 
is  to  take  oxygen  into  the  body.  Of  food,  we  have  enough 
stored  in  the  body  to  maintain  life  for  a  number  of  days, 
or,  in  some  cases,  even  for  several  weeks.  As  to 
oxygen,  however,  the  body  leads  a  hand-to-mouth 
existence  ;  for  though  the  air  is  more  than  one  fifth 
oxygen,  there  is  not  enough  of  this  gas  in  the  body  to 
keep  us  alive  for  more  than  two  or  three  minutes 
after  breathing  has  stopped.  While  we  sleep,  there- 
fore, "we  must  keep  on  breathing  in  oxygen;  sit  as  quiet 
as  we  may,  we  must  still  keep  on  taking  it  in ;  and  when 
we  walk  or  run,  we  do  it  taking  in  oxygen  as  we  go. 
The  second  object  of  respiration  is  to  give  off  carbon 

53 


F1G' 


54 


PRIMER   OF  PHYSIOLOGY 


dioxidfrom  the  body.     Carbon  dioxid  is  a  waste  gas  that 
is  all  the  time  being  formed  in  the  cells  and  carried  by 

the  blood  to  the  lungs, 
to  be  breathed  out  into 
the  air.  It  is  formed 
not  only  in  the  body, 
but  where  wood,  coal, 
oil,  or  gas  is  burned, 
and  it  is  sometimes 
found  in  coal  mines, 
where  it  is  known  to 
the  miners  as  "choke 
damp." 

FIG.  55.      The  chest,  showing  the  position  of       The     Cavity     Of      the 

the  heart  and  lungs. 


the  chest  contains  the  heart  and  the  lungs.  This  cavity 
is  inclosed  by  the  ribs  and  sternum,  and  is  separated 
from  the  abdominal  cavity  below  by  a  thin  cross-parti- 
tion called  the  diaphragm.  In  breathing,  the  chest  cav- 
ity is  enlarged  by  lifting  the  ribs  upward  and  outward, 
and  by  pulling  the  diaphragm  downward. 

The  trachea  and  the  lungs.  The  trachea  has  in  its 
walls  stiff  rings  of  cartilage  that  hold  it  open  so  that  the 
air  can  pass  freely  through  it  to  and  from  the  lungs. 
At  its  base  the  trachea  divides  and  sends  a  great  branch 
to  each  lung.  Within  the  lungs  these  branches  divide 
again  and  again,  until  finally  they  end  in  little,  thin- 
walled  air  sacs.  The  branches  of  the  trachea  are  called 
the  bronchial  tubes,  and  the  lungs  have  a  light,  spongy 
texture  because  they  are  composed  chiefly  of  these  tubes 
and  of  the  air  sacs  in  which  the  tubes  end. 

The  changes  in  the  air  in  the  lungs.     The  walls  of  the 


RESPIRATION' 


55 


air  sacs  are  very  thin,  and  great  numbers  of  small  blood 
streams  constantly  flow  through  the  capillaries  in  them. 
The  oxygen  of  the  air  that  we  take  into  the  lungs 
passes  into  the  blood  through  the  walls  of  the  sacs,  and 


trachea 


lung 


air  sacs 


bronchial  tube 

FIG.  56.      The  lungs. 

the  carbon  dioxid  that  is  in  the  blood  passes  out  into  the 
air  that  is  in  the  sacs,  and  is  then  breathed  out  of  the 
lungs.  The  air  in  the  lungs,  therefore,  loses  oxygen  and 
gains  carbon  dioxid,  and  the  blood  takes  in  oxygen  and 
gives  up  its  carbon  dioxid. 


PRIMER   OF  PHYSIOLOGY 


These  changes  take  place  very  rapidly  in  the  lungs, 
for  the  capillaries  are  so  numerous  that  they  cover  more 
than  one  third  of  the  surface  of  the  air  sacs,  and  all  the 
blood  in  the  body  goes  through  them  in  a  little  over  a 
minute. 

Injury  done  to  the  respiratory  organs 
by  dust.     Nearly  all  the  diseases  of  the 
air  passages  and  lungs  are  caused  by 
germs.     Dust  wounds  and  injures  the 
FIG.  57.     A   s  m  a 1 1  delicate  lining  of  these  parts,  and  makes 

bronchial  tube  and  the    . 

air  sacs  in  which  it  it  easy  for  germs  to  gain  an  entrance 
ends-  into  the  tissues.     The  majority  of  work- 

men in  certain  industries,  such  as  metal  grinders,  pot- 
ters, and  workers  in  cotton  and  woolen  mills,  die  of 
pneumonia,  tuberculosis,  and  other  respiratory  diseases. 
This  is  due  to  the  multitude  of 
tiny  wounds  continually  being 
made  in  the  walls  of  the  air 
passages  by  the  sharp  dust 
and  fine  fibers  with  which  the 
air  of  many  factories  and  mills 
is  laden.  Much  can  be  done 
to  make  dusty  trades  more 
healthful  by  using  water  in 
operations  where  dust  is 
formed,  by  hoods  and  air 
blasts  that  suck  up  the  dust 
from  machines,  and  by  the  FlG-  58.  A  workman  wearing  a 

mouthpiece    to     protect    himself 

workmen   wearing    appliances  from  dust.    (From  a  photograph 

tO  protect  themselves  from  the    %  the  Massachusetts  State  Board 

dust. 
Sweeping  without  raising  a  dust.     In   many  states 


RESPIRATION' 


57 


IJIfl  illlSSStl 


dry  sweeping  of  school  buildings  and  of  other  public 
buildings  is  forbidden  by  law,  because  it  stirs  up  great 
quantities  of  dust,  which  then  remains  floating  in  the 
air  for  hours.  The  best  method  of  cleaning  public 
buildings,  as  well  as  private  homes,  is  the  vacuum  pro- 
cess. When  this  cannot  be  used,  wet  sawdust,  a  sweep- 
ing compound,  or  something 
else  effective  should  be  em- 
ployed to  keep  down  the  dust. 
One  device  that  is  sometimes 
used  is  a  can  attached  to  the 
handle  of  a  broom  and  so  ar- 
ranged that  it  keeps  the  broom 
moist  with  kerosene  or  water. 

FlG.  59.    A  dustless  brush.     The 

The  floor  brush  shown  in  Fig-  back  of  the  brush  is  hollow  and 
ure  59  is  very  satisfactory  for  is   filled  with  kerosene,  which 

~.  rc  ..     .      slowly  trickles  down  and  keeps 

sweeping,  and  pararhn  oil  is  the  bristles  moist  while  the  sweep, 
extensively  used  in  making  up  ing  is  being  done, 
floor  dressings  and  sweeping  compounds.  This  oil  may 
be  purchased  for  ten  cents  a  quart,  or  at  a  lower  price 
in  larger  quantities,  and  it  gives  an  excellent  polish .  to 
floors  and  furniture.  Sawdust  moistened  with  it  makes 
a  very  satisfactory  sweeping  compound,  and  a  cloth 
dampened  with  it  is  the  best  thing  for  removing  dust 
from  furniture  and  for  cleaning  doors. 

Gaseous  impurities  in  the  air.  In  many  houses  small 
quantities  of  gas  are  constantly  escaping  from  the  pipes, 
and  often  this  leaking  of  gas  is  allowed  to  run  on 
for  weeks  and  months  before  the  pipes  are  repaired. 
Breathing  this  gas,  especially  if  it  is  water  gas,  is  most 
injurious  to  the  health.  Another  most  harmful  practice 
is  the  use  of  gas  and  oil  stoves  that  have  no  pipes  to 


58  PRIMER  OF  PHYSIOLOGY 

carry  away  the  fumes ;  for  it  is  ruinous  to  the  health 
to  breathe  the  poisonous  gases  that  come  from  them. 

The  effect  of  tobacco  on  the  respiratory  organs.  To- 
bacco smoke  is  hot  and  irritating  and  often  causes  sore 
tongue  and  "  smoker's  sore  throat."  Undoubtedly  these 
diseases  sometimes  lead  to  cancer,  because  any  part  of 
the  tissues  that  is  constantly  irritated  may  develop  into 
a  cancer.  When  the  smoke  is  inhaled  into  the  lungs  a 
sooty  deposit  which  must  certainly  be  injurious  is  left  on 
the  walls  of  the  bronchial  tubes.1  When  smoke  is  ex- 
haled through  the  nose  it  has  a  tendency  to  cause  ca- 
tarrh and  injures  the  sense  of  smell.  The  nicotin  that 
is  taken  into  the  blood,  either  by  partially  paralyzing 
the  nerve  centers  that  control  the  breathing  muscles, 
or  by  its  effect  on  the  muscles  themselves,  causes  the 
shortness  of  breath  with  which  every  smoker  who  has 
tried  to  take  part  in  athletic  sports  is  familiar. 

QUESTIONS 

Why  will  a  plant  die  if  its  roots  are  in  boiled  water?  What 
is  the  first  object  of  respiration?  Why  can  a  person  live  a 
long  time  without  eating,  but  only  a  few  minutes  without 
breathing?  What  is  the  second  object  of  respiration? 

What  organs  are  in  the  cavity  of  the  chest  ?  By  what  is  the 
chest  inclosed?  How  is  the  chest  cavity  enlarged  in  breath- 
ing? Describe  the  trachea  and  its  branches.  How  do  the 
bronchial  tubes  end  ?  Explain  the  changes  that  take  place  in 
the  air  in  the  lungs. 

1  "  Surely  smoke  becomes  a  kitchen  far  better  than  a  dining  chamber, 
and  yet  it  makes  a  kitchen  oftentime  in  the  inward  parts  of  man,  soyling 
and  infecting  them  with  an  oyly  kind  of  soote  as  hath  been  found  in  some 
great  tobacco  takers,  that  after  their  death  were  opened."  —  KING  JAMES  I. 


RESPIRATION  59 

Why  is  breathing  dust  dangerous?  What  may  be  done  to 
keep  down  dust  in  factories?  How  may  buildings  be  swept 
without  raising  a  dust?  Why  should  leaks  in  gas  pipes  in 
houses  be  carefully  looked  after?  Why  is  it  injurious  to  use 
gas  or  oil  stoves  that  have  no  pipes  to  carry  away  the  gases? 

SUGGESTIONS  TO  THE  TEACHER 

Have  a  pupil  breathe  through  a  glass  tube  into  limewater.  The 
white  precipitate  is  calcium  carbonate,  which  is  formed  by  the  union 
of  the  carbon  dioxid  with  the  calcium  in  the  limewater. 

Call  attention  to  the  dust  particles  which  may  be  seen  floating  in 
the  air  when  a  beam  of  sunlight  penetrates  a  darkened  room.  Use 
all  possible  influence  to  have  the  school  building  swept  and  dusted 
in  a  sanitary  manner.  Call  attention  to  the  importance  of  hygienic 
industrial  conditions  and  to  the  fact  that,  in  selecting  an  occupation, 
the  effect  of  the  work  on  the  health  is  as  deserving  of  consideration 
as  the  wages  that  may  be  earned. 


CHAPTER   SEVEN 

VENTILATION 


FIG.  60.     Move  your  bed  out  into  the  open  air  if  it  is  possible  for  you  to  do  so. 

IN  1/58,  during  a  rebellion  of  the  native  soldiers  in 
India,  one  hundred  and  forty-six  Englishmen  were  shut 
up  overnight  in  a  room  that  had  but  a  single  window. 
When  morning  came,  only  twenty-three  of  them  re- 
mained alive.  After  the  battle  of  Austerlitz,  three 
hundred  prisoners  were  crowded  into  a  cavern.  In  a 
few  hours  two  thirds  of  them  were  dead.  Many  other 
instances  are  on  record  of  people  who  have  perished 
when  shut  up  in  closets,  vaults,  or  the  holds  of  ships. 
Most  persons  have  read  of  some  of  these  instances,  and 
practically  every  one  takes  care  to  keep  out  of  places 
where  he  is  likely  to  perish  because  his  supply  of  air 
fails. 

60 


VENTILATION  6 1 

It  would  seem,  however,  that  many  persons  are  like 
the  kind-hearted  old  gentleman  who  could  not  bring 
himself  to  cut  his  dog's  tail  off  all  at  once,  and  so  cut 
off  an  inch  each  morning  until  the  tail  was  gone ;  for 
while  these  people  object  most  decidedly  to  killing  their 
bodies  all  at  once  with  bad  air,  they  do  not  seem  to 
mind  killing  them  a  little  at  a  time.  Perhaps  they  do 
not  realize  what  they  are  really  doing,  but  the  damage 
is  constantly  being  done,  nevertheless ;  for  they  go  to 
churches,  lecture  halls,  and  theaters  where  the  air  is 
so  foul  that  it  gives  them  headaches;  many  persons 
sleep  in  rooms  with  windows  and  doors  so  tightly 
closed  that  the  sleepers  must  breathe  the  same  air 
again  and  again ;  children  often  cover  their  heads  with 
the  bedclothes  and  do  not  get  a  breath  of  fresh  air  all 
night  long;  and  many  schools  and  factories  are  so 
badly  ventilated  that  the  health  and  the  working  power 
of  those  in  them  are  continually  being  undermined. 
The  whole  subject  of  ventilation  is,  therefore,  of  the 
very  greatest  importance,  and  in  this  chapter  we  shall 
take  up  the  study  of  why  we  need  fresh  air  and  how 
to  get  it. 

Enough  oxygen  usually  in  the  air.  About  one  fifth 
(21  per  cent)  of  the  air  is  oxygen,  and  the  remainder  is 
nearly  all  nitrogen.  The  nitrogen  is  not  used  in  the 
body,  but  is  simply  breathed  into  the  lungs  and  breathed 
out  again  unchanged.  The  oxygen  is  taken  into  the 
blood  and  carried  through  the  body  to  the  cells.  Air 
that  has  been  breathed  once  has  lost  about  one  fourth 
of  its  oxygen,  and  where  people  are  crowded  together 
as  the  English  were  in  the  "  Black  Hole  of  Calcutta," 
the  oxygen  in  the  air  becomes  exhausted.  We  can  live, 


62 


PRIMER   OF  PHYSIOLOGY 


however,  on  15  or  even  on  12  per  cent  of  oxygen, 
and  under  any  ordinary  conditions  the  trouble  with 
the  air  we  breathe  is  not  with  the  amount  of 
oxygen  in  it. 

The  carbon  dioxid  problem.     Carbon  dioxid  is  given 
off  into  the  air  from  the  lungs,  and  too  much  of  it  in 


FIG.  61.      An  outdoor  lesson  in  geography.    (After  'Ayres.) 

the  air  is  poisonous  to  us.  It  was  long  supposed  that 
this  was  the  chief  trouble  with  indoor  air, — that  the 
paleness  and  lack  of  strength  noticed  in  those  who  lived 
without  .good  ventilation  were  due  to  carbon  dioxid 
poisoning.  All  our  rules  for  ventilating  buildings  have 
been  laid  down  with  the  idea  that  we  must  bring  in 
large  quantities  of  fresh  air  (3000  cubic  feet  per  hour 
for  each  person)  to  keep  the  carbon  dioxid  from  be- 
coming too  abundant  in  the  air  that  we  breathe.  This 
is  still  a  good  rule  to  follow ;  for  it  has  not  yet  been 
proved  that  breathing  large  amounts  of  carbon  dioxid 
week  after  week  is  not  injurious  to  the  health.  Re- 
cently, however,  it  has  been  proved  that  in  ventilation 


VENTILATION 


other  questions  besides  the  amount  of  carbon  dioxid  in 
the  air  must  be  considered. 

Dry  air  injurious.  In  rooms  heated  by  stoves,  radi- 
ators, or  hot-air,  systems,  the  atmosphere  becomes  too 
dry,  unless  special  arrangements  are 
made  for  moistening  it,  —  drier,  in 
fact,  than  is  the  air  in  the  Desert 
of  Sahara.  Since  dry  air  quickly 
evaporates  the  sweat  from  the  skin 
and  cools  the  body,  people  often 
heat  such  rooms  up  to  75  or  80  de- 
grees, because  they  feel  cold  at  lower 
temperatures. 

Living  in  a  hot,  dry  atmosphere  of 
this  kind  is  injurious  to  the  eyes,  and 
it  makes  people  subject  to  colds;  it  FIG.  62.   A  home-made 
causes  nervousness,  also,  and  a  child  humidifier  -  a  Paii  with 

a  strip  of  cloth  arranged 

in  a  dry,   overheated  schoolroom  is  for  feeding  the  water  up 

h  evaP°rate 


restless  and  has  difficulty  in  keeping 
his  mind  on  his  work.  Vessels  of 
water  should  therefore  be  kept  in  furnaces  and  on  stoves 
and  radiators;  and  in  school  buildings  heated  with  hot 
air,  arrangements  should  be  made  to  moisten  the  air  be- 
fore it  is  discharged  into  the  rooms.  It  is  economy  to 
give  attention  to  this  point  ;  for  moist  air  feels  as  warm 
at  65  degrees  as  dry  air  at  75  degrees  ;  in  some  school 
buildings  as  much  as  a  10  per  cent  saving  in  fuel  has 
followed  the  installation  of  devices  for  moistening  the 
air. 

A  moist  atmosphere  and  overheating.  When  the  tem- 
perature of  moist  air  rises  much  above  70  degrees,  it 
gives  us  a  hot,  suffocating  feeling,  similar  to  that 


64  PRIMER  OF  PHYSIOLOGY 

which  one  has  on  a  warm,  sultry  summer  morning.  The 
explanation  of  this  is  that  the  moisture  in  the  air  keeps 
the  sweat  from  evaporating,  and  there  is  a  layer  of  hot, 
wet  air  surrounding  the  body  like  a  shell.  In  crowded 
buildings,  therefore,  where  the  air  is  wet  from  many 
people  breathing  it,  a  proper  temperature  is  very  im- 
portant. It  ought  not  to  fall  below  65  degrees,  for  then 
the  people  will  be  chilly ;  and  it  ought  not  to  run  above 
70  degrees,  for  then  the  people  will  become  hot  and  un- 
comfortable, some  of  them  will  develop  headaches,  and 
many  of  them  will  catch  cold  when  they  step  out  into 
the  cool  outside  air. 

The  necessity  for  motion  in  the  air.  In  hot  weather, 
and  in  warm  and  wet  indoor  atmospheres,  it  is  most 
important  that  there  be  air  currents  to  break  up  and 
blow  away  the  hot,  moist  air  blankets  that  surround  us. 
How  important  such  air  currents  are,  is  shown  by  an 
experiment  that  was  carried  out  in  England.  In  this 
experiment,  a  group  of  students  were  closed  in  a  small 
room  and  watched  through  a  glass  in  the  door.  At 
first  they  were  laughing  and  joking,  but  soon  they  began 
to  show  signs  of  distress.  Formerly  it  would  have 
been  concluded  that  they  were  suffering  from  a  lack  of 
oxygen  or  were  being  poisoned  by  carbon  dioxid.  The 
real  trouble,  however,  was  the  overheating  and  the  mois- 
ture in  the  air,  as  was  proved  by  the  fact  that  when  an 
electric  fan  was  started  in  the  room,  the  students  be- 
came comfortable  again  without  the  introduction  of  fresh 
air. 

Setting  indoor  air  in  motion.  In  public  buildings  the 
air  often  becomes  close  and  the  temperature  rises  after 
meetings  have  been  in  progress  for  some  time.  In  such 


VENTILATION 


cases  a  great  deal  can  be  done  towards  keeping  the 
audience  comfortable  by  opening  a  few  windows,  so 
that  part  of  the  heated  air  will  escape  and  currents  will 
be  set  up  through  the  building. 
In  the  Chicago  schools,  every 
window  in  every  schoolroom  is 
thrown  wide  open  three  times 
a  day  to  allow  the  wind  to 
sweep  out  the  stale  air  in  the 
buildings  and  to  break  up  and 
blow  away  the  envelopes  of 
moist  air  from  about  the  bodies 
of  the  pupils.  Practices  like 
this  should  be  followed  every- 
where. A  few  minutes  de-  __ \ 
voted  to  flushing  out  a  school-  // /  /  /  /  // 
room  and  going  through  a  few  FIG  63.  A  window  board  helps 
resting  and  stretching  exer-  to  ventilate  a  room, 
cises  are  by  no  means  to  be  counted  as  lost,  for  the 
pupils  return  to  their  work  with  new  vigor  and  zeal. 

It  is  well  to  understand  also  that  the  health  of  many 
workers  could  be  improved  and  their  working  power 
greatly  increased  by  providing  them  with  electric  fans 
during  the  hot  summer  weather.  Many  factory  owners 
who  have  put  in  ventilating  systems  have  found  "that  the 
increased  amount  of  work  accomplished  by  the  laborers 
in  the  factory  far  more  than  paid  the  cost  of  putting  in 
and  operating  the  system.  This  is  what  we  should  ex- 
pect, for  every  one  knows  the  difficulty  of  working  in 
an  overheated,  stifling  atmosphere,  and  how  bracing 
and  invigorating  a  current  of  air  is  on  a  hot,  oppres- 
sive day. 


66 


PRIMER   OF  PHYSIOLOGY 


Disagreeable  odors  in  crowded   rooms.     In   crowded 
and  heated  rooms,  odors  always  arise  that  cause  head- 
ache and  a  feeling  of  faintness  in  persons  who  are  sen- 
sitive to  them.     A  low 
temperature       makes 
these  odors  much  less 
noticeable,  and  a  cur- 
rent   of    fresh    air 
through  the  room  not 
only  sweeps  away  the 

FIG.  64.  An  open-air  schoolroom  in  Sacra-  odors  themselves,  but 
mento,  California.  The  inclosed  room  is  aicrk  v^fr-^cV^c  fl->^ 
used  only  in  bad  weather. 

people    and    destroys 

the  effects  of  the  odors  on  them.  Persons  who  are 
troubled  with  symptoms  of  illness  when  they  attend 
public  meetings  can  sometimes  escape  the  difficulty  by 
arranging  for  a  seat  near  a  ventilator  or  window,  or 
where  a  current  of  air  from  an  open  doorway  will  blow 
across  them.  It  is  probable  that  "crowd  poisoning" 
is  nothing  but  the  effect  of  the  overheating  and  of  the 
odors  that  are  usual  in  buildings  where  many  people  are 
assembled. 

Open-air  schools.  In  Oakland,  California,  during  the 
winter  of  1910—191 1,  an  open-air  school  was  in  operation. 
In  this  School  the  children  did  regular  work,  and  they  had 
no  special  feeding  or  rest  periods.  Yet  during  the  first 
half  year  no  child  in  the  school  failed  to  gain  in  weight, 
and  the  average  gain  was  3.70  pounds;  in  the  regular 
school  building  the  average  gain  was  2.36  pounds.  The 
children  in  the  open-air  school  were  free  from  colds, 
while,  as  usual,  the  children  in  the  indoor  school  at  times 
suffered  from  them.  Most  noticeable  of  all,  however. 


VENTILATION-  67 

was  the  wide-awake,  energetic  way  in  which  the  open-air 
pupils  kept  at  their  work.  Day  after  day  they  finished 
their  tasks  without  becoming  tired,  and  by  the  end  of 
the  year  all  of  them  had  advanced  one  grade,  several  of 


FlG.  65.  An  outdoor  classroom  at  Williamsburg,  Virginia.  When  the 
children  become  tired  indoors,  classes  are  taken  to  this  building  for  a  recitation. 
There  were  only  20  days  during  the  winter  of  1911-1912  on  which  this  outdoor 
classroom  was  not  used. 

them  had  advanced  two  grades,  and  one  boy  had  done 
two  and  one  half  years'  work  in  the  one  year. 

In  many  places  open-air  schools  have  been  established 
for  sick  children,  with  the  idea  of  nursing  them  back  to 
health  rather  than  of  advancing  them  in  their  school 
work.  In  these  schools  the  pupils  are  fed  and  have 
long  rest  periods,  and  only  light  school  work  is  done. 
Experience  has  shown,  however,  that  in  the  open  air 
the  children  throw  themselves  into  the  work  so  eagerly 
and  their  minds  are  so  clear  that  even  in  outdoor  schools 
that  give  only  half  the  usual  time  to  study,  the  pupils 
advance  as  rapidly  as  they  do  in  an  indoor  school 
where  they  spend  the  whole  day  over  their  books. 


68 


PRIMER   OF  PHYSIOLOGY 


the  Horace  Mann  Elementary  School,  Teachers 
College,  New  York. 


Why,  then,  should  not  boys  and  girls  who  are  in  good 
health,  as  well  as  those  who  are  sick,  be  in  schools  where 
they  can  master  their  work  with  the  greatest  ease  and 
at  the  same  time  build  up  their  bodies  by  breathing  out- 
door air  ?  The  time 
has  come  when  each 
community  must  an- 
swer this  question. 
In  mild  climates  and 
in  warm  weather, 
there  is  certainly  no 
reason  for  going  to 
the  great  expense  of 

FIG.  66.    Open-air  classes  held  on  the  roof  of   trying  to  get  the  right 

kind  of  air  indoors, 
when  nature  has  filled 
all  outdoors  with  exactly  the  kind  of  invigorating  air 
that  we  need. 

Outdoor  sleeping.  In  recent  years  thousands  of  out- 
door sleeping  porches  have  been  built  in  our  country. 
Without  a  doubt  the  health  is  greatly  benefited  by 
passing  in  the  open  air  the  many  hours  that  we 
spend  in  sleep.  The  only  point  that  needs  to  be  re- 
membered in  moving  outdoors  is  that  the  warmth  of 
the  body  must  be  kept  up ;  that  man  moved  into  houses 
to  protect  himself  from  the  cold  and  wet,  and  when 
he  moves  out  of  them  again  he  must  have  clothing  that 
will  keep  him  warm  and  dry.  If  this  point  is  looked 
after,  the  more  time  we  spend  outdoors  the  better. 
Therefore,  move  out  into  the  outdoor  air  to  sleep  if  you 
can,  and  if  you  cannot  do  this,  open  wide  the  windows 
of  your  bedroom  and  let  the  outdoor  air  come  to  you. 


VENTILATION"  69 

QUESTIONS 

What  two  gases  make  up  the  greater  part  of  the  air  ?  Which 
of  these  gases  is  used  by  the  body?  Under  what  conditions 
may  the  oxygen  supply  of  the  air  become  exhausted  ? 

What  is  carbon  dioxid  ?  How  much  fresh  air  is  supposed 
to  be  needed  by  each  person  in  a  building  ?  Why  does  dry 
air  cause  a  sensation  of  chilliness  ?  What  bad  effects  follow 
living  in  a  dry  atmosphere?  Is  there  any  method  of  moisten- 
ing the  air  used  in  your  school  building  or  in  your  home? 
Explain  how  it  works. 

Why  does  one  easily  become  overheated  in  a  moist  atmos- 
phere? Describe  an  experiment  that  proved  the  importance 
of  keeping  the  air  in  motion.  Mention  some  ways  by  which 
air  currents  may  be  set  up  in  buildings.  In  what  way  have 
factory  owners  been  repaid  for  the  cost  of  installing  and 
operating  ventilating  systems? 

What  effects  have  the  odors  of  crowded  rooms  on  certain 
persons?  What  may  be  done  to  make  these  odors  less  notice- 
able ? 

Give  an  account  of  the  open-air  school  at  Oakland,  Califor- 
nia. For  what  purpose  are  open-air  schools  used  in  many 
places?  What  advancement  do  the  pupils  in  these  schools 
make  in  their  school  work?  In  outdoor  life  what  point  must 
be  kept  in  mind  ? 

SUGGESTIONS  TO  THE  TEACHER 

Give  gymnastic  exercises  while  the  schoolroom  windows  are 
opened.  Insist  on  the  importance  of  the  pupils  putting  their  knowl- 
edge of  ventilation  into  practical  use  in  their  home  life. 

Perform  for  the  class  experiments  with  wet-  and  dry-bulb  ther- 
mometers (consult  Appendix  of  Human  Physiology}.  Bring  out  that 
because  the  skin  is  kept  moist  by  the  perspiration  the  body  is  com- 
parable to  a  wet-bulb  thermometer,  and  that  it  is  the  wet-bulb  rather 
than  the  dry-bulb  temperature  that  is  important  in  regulating  the 
temperature  of  rooms. 


CHAPTER   EIGHT 

ADENOIDS  AND  COLDS 


FIG.  67.  Adenoids  sap  the  strength  so  that  any  one  who  is  suffering  from 
them  has  very  little  chance  of  being  the  best  athlete  in  the  school ;  they  dull  the 
mind  so  that  the  victim  of  them  rarely  stands  at  the  head  of  his  class. 


AMONG  the  most  common  of  all  the  ailments  that 
afflict  the  inhabitants  of  the  temperate  and  frigid  re- 
gions of  the  earth,  are  colds  and  certain  other  troubles 
of  the  nose  and  throat.  These  maladies,  of  course,  are 
not  so  severe  as  many  other  diseases,  but  certainly  they 
cause  more  inconvenience  than  all  our  other  lesser  sick- 
nesses combined.  It  is  true  also  that  they  often  weaken 
the  body  and  lay  the  foundations  for  other  serious  diffi- 
culties. People  lack  the  general  understanding  of  these 
diseases  that  they  ought  to  have,  and  in  this  chapter  we 
shall  therefore  make  a  study  of  them.  In  order  that 
we  may  do  so  more  intelligently,  we  shall  first  consider 
the  structure  of  the  nose  and  throat. 

The  chambers  of  the  nose.  The  air  passes  through 
the  nostrils  into  the  nasal  chambers.  These  long,  nar- 
row passages  are  about  three  quarters  of  an  inch  wide ; 

70 


ADENOIDS  AND   COLDS 


-I 

FIG.  68.  A  cross-section  of  the 
nasal  chambers,  showing  the  bones 
(a,  b,  and  c)  that  stand  out  in  the 
pathway  of  the  air.  The  mucous 
membrane  lining  the  chambers  is 
shown  in  white. 


they  extend  up  into  the  head  about  as  high  as  the  level 
of  the  eyes,  and  they  run  back  and  open  into  the  throat 
behind  the  mouth.  They  are 
separated  from  each  other  by 
a  very  thin,  bony  partition. 
On  the  outer  wall  of  each 
chamber  are  three  curved  and 
rolled-up  bones  that  stand  out 
in  the  pathway  of  the  air  (Fig. 
68).  The  whole  interior  of 
the  nasal  chambers  is  lined  by 
the  same  skin-like  mucous 
membrane  that  is  found  in  the 
mouth  and  throat.  This  is 
kept  moist  by  a  sticky  sub- 
stance called  mucus. 

The  air  warmed  and  cleansed  in  the  nose.  The  air  in 
the  nose  comes  in  contact  with  the  lining  of  the  chambers, 
and  is  drawn  in  among  the  bones  that  stand  out  in  the 
nasal  passages.  In  this  way  the  air  is  warmed,  and  the 
dust  and  germs  in  it  are  caught  on  the  moist,  sticky 
mucous  membrane  that  lines  the  cavities  and  covers  the 
bones.  The  function  of  the  nose  in  respiration  is  to  protect 
the  throat  and  lungs  from  cold  and  from  dust  and  germs. 

Troubles  in  the  nose.  Sometimes  the  thin  partition 
between  the  two  sides  of  the  nose  becomes  bent  so  that 
it  closes  one  of  the  nasal  chambers;  sometimes  the 
bones  in  the  nose  enlarge  until  they  interfere  with  the 
breathing  and  prevent  the  proper  drainage  of  the  nose; 
and  in  a  considerable  number  of  persons,  swollen  and  over- 
grown portions  of  the  mucous  membrane,  called  nasal 
polyps,  block  the  air  passages.  In  all  such  cases,  the 


PRIMER  OF  PHYSIOLOGY 


Eustachian  tube 
soft  palate 

position  of 
adenoids 
tonsil 


obstruction  in  the  nose  ought  to  be  removed  by  a  physi. 
cian  who  understands  how  to  do  the  work.  If  this  is  not 
done,  the  breathing  will  be  interfered  with  continually, 
and  colds  and  chronic  catarrh  are  likely  to  be  the  result. 
The  throat.  The  throat  is  a  funnel-shaped  cavity 
which  curves  backward  and  downward  around  the  base 

of  the  tongue. 
At  its  bottom  are 
two  openings,  one 
leading  to  the 
stomach  and  one 
leading  to  the 
lungs.  In  front, 
a  little  flap-like 
structure,  the  soft 
palate,  hangs 
down  from  above 
and  partly  sepa- 
rates the  throat 
from  the  mouth. 
Above  and  behind 
the  soft  palate 
are  two  openings 
which  lead  into 

the  nose,  and  high  up  in  the  walls  on  either  side  of  the 
throat  are  the  mouths  of  the  two  Eustachian  tubes, 
which  are  small  passageways  that  lead  to  the  middle 
ears  (Fig.  69).  In  the  walls  of  the  throat  are  four 
tonsils,  which  we  shall  describe  in  some  detail. 

The  tonsils.  One  small  tonsil  lies  in  the  back  of  the 
tongue ;  one  is  high  up  in  the  back  wall  of  the  throat ; 
and  the  other  two  lie  in  the  side  walls  of  the  throat. 


FlG.  69.    The  nasal  passages,  mouth,  and  throat. 


ADENOIDS  AND   COLDS 


Fi3.  70.    A  ton- 
sil.     A  part  of  the 


These  structures  are  composed  of  loose,  spongy  tissue, 

and  leading  down  into  them  are  small  openings,  or  crypts, 

which  are  formed  by  folding  the  mucous  membrane  down 

into  deep  little  pockets  (Fig.  70).     Germs 

grow  in  these  pockets  and  cause  tonsillitis, 

—  a  disease  in  which  the  tonsils  are  swollen 

and  have  matter  in  them  like  that  found 

in  boils.     In  many  persons  the  tonsils  are 

always  infected  with  germs  and  become  so 

swollen  and  enlarged  that  they  block  the 

throat   and   interfere  with  the  breathing. 

The   tonsil  which  is  most  commonly  en-   tonsil  is  cut  away 

,        ,  •      ,  ,,       r  to  show  a  crypt. 

larged  is  the  one  in  the  back  wall  of  the 
throat,  and  the  spongy,  swollen,  whitish  mass  of  soft 
tissue  into  which  this  tonsil  changes  is  called  adenoids,  or 
adenoid  growths.  Usually,  when  adenoids  are  present, 
the  other  tonsils  also  are  enlarged,  but  this  is  not 
always  the  case. 

The 'symptoms  of  adenoids.  In  moist  climates  one 
fourth  of  all  the  children  may  have  adenoids.  The  most 
easily  recognized  symptom  of  them 
is  mouth  breathing.  If  the  throat 
is  entirely  blocked  by  them  and  the 
tonsils  also  are  enlarged,  the  mouth 
will  be  kept  open  so  wide  that  any 
one  will  notice  that  the  child  is  a 
mouth  breather.  If  the  throat  is 
only  partly  filled,  the  child  may  keep 
his  mouth  open  only  a  little,  and  the 
mouth  breathing  may  not  be  noticed 
*  all,  except  when  the  child  has  a 
\After  Wingravc.)  cold  or  is  asleep.  After  the  adenoids 


74  PRIMER   OF  PHYSIOLOGY 

have  been  growing  for  some  time,  the  upper  teeth  begin 
to  turn  forward  ;  the  face  is  puffed  out  under  the  eyes  ; 
the  eyes  have  a  strained  look  and  are  drawn  down  at 
the  inner  corners  ;  the  lips  thicken  ;  the  upper  lip 
shortens  and  is  turned  out;  there  is 
often  a  white  line  running  down  from 
the  corner  of  the  nose  marking  off  the 
division  between  the  cheek  and  lip;  and 
the  whole  face  has  a  dull,  stupid  look. 

FIG.  7         Adenoid  In    many    CaSeS    °f    aden°id    growths, 

growth  that  has  been    the  germs  work  their  way  up  the  Eusta- 

removed.     One  half     chjan    tubes    and    cause    earacne,    which 
natural  size.    {After 

1S  an  almost  certain  symptom  of  them. 


They  also  interfere  with  speech,  and  any 
one  who  "  talks  through  his  nose  "  or  has  difficulty  in 
pronouncing  his  words  clearly,  probably  has  his  nasal 
passages  blocked  by  them.  A  child  with  this  trouble 
usually  snores,  and  in  bad  cases  sometimes  gasps  and 
struggles  for  breath  during  sleep. 

Besides  these  symptoms  of  adenoid  growths,  there  are 
certain  other  effects  that  often  go  with  them.  Sometimes 
children  who  have  them  are  very  restless  and  nervous, 
and  are  unable  to  keep  their  attention  fixed  on  any  one 
thing.  Often  they  are  stupid  at  their  books  and  fall 
behind  in  their  school  work.  Usually  the  digestion  is 
disordered  from  swallowing  the  multitudes  of  germs 
that  come,  from  the  adenoid  and  tonsils.  Often  the 
chest  is  narrow  and  the  child  is  undersized,  —  some- 
times two  or  three  years  smaller  than  he  should  be. 
Another  effect  of  adenoids,  very  noticeable  in  some 
cases,  is  a  fretful,  quarrelsome,  and  seemingly  perverse 
disposition,  —  a  lack  of  self-control  and  a  tendency  to 


ADENOIDS  AND   COLDS 


75 


fly  into  a  rage  at  the  slightest  provocation.  This  causes 
the  victim  to  make  trouble  for  his  parents,  for  his  teacher, 
and  for  all  who  have  anything  to  do  with  him. 

The  remedy  for  adenoid  growths  and  infected  tonsils. 
The  only  thing  to  do  for  adenoids  and  infected  tonsils  is 
to  have  them  out  at  once.  When  performed  by  a  skilled 


FIG.  73.    Typical  adenoid  faces. 

surgeon  this  operation  is  not  severe,  and  in  thousands  of 
cases  it  has  resulted  in  an  improvement  in  the  condition 
of  the  child  that  is  almost  miraculous.  One  sixteen-year- 
old  boy  gained  fourteen  pounds  in  three  weeks  after  hav- 
ing his  adenoids  and  tonsils  removed  ;  and  it  is  a  common 
thing  for  a  child  whose  adenoid  growths  have  been  taken 
out  to  make  a  sudden  increase  in  height  and  weight  and 
to  renew  his  interest  in  his  school  work. 

The  evil  consequences  of  waiting  to  outgrow  adenoids. 
Usually,  but  not  always,  adenoids  disappear  by  the  time 


76  PRIMER   OF  PHYSIOLOGY 

a  person  is  grown.1  It  must  not  be  thought,  however, 
that  their  evil  effects  disappear  with  them ;  for  if  the 
nostrils  are  not  used  in  breathing,  the  nasal  chambers 
and  the  upper  part  of  the  face  do  not  grow  as  they 
should,  and  the  person  is  left  with  narrow  air  passages, 
protruding  upper  teeth,  a  short,  thick  upper  lip,  and 
often  with  a  catarrh  and  a  swollen  condition  of  the  nasal 
mucous  membrane  that  will  remain  with  him  for  life. 
Neglected  adenoids  spoil  the  beauty  of  the  face  for  all 
time,  and  it  is  estimated  that  three  fourths  of  all  deaf- 
ness is  due  to  them.  Any  one  who  advises  waiting  to 
outgrow  adenoids  is  giving  the  worst  advice  possible. 
They  ought  to  be  removed,  and  this  ought  to  be  done  be- 
fore they  interfere  with  the  growth  of  the  bones  of  the 
nose  and  face. 

Colds.  Colds  are  caused  by  germs  that  live  on  the 
mucous  membrane  of  the  nose  and  throat.  They  may 
be  divided  into  two  classes,  —  epidemic  colds  and  chronic 
colds.  Epidemic  colds  are  caused  by  germs  of  a  particu- 
larly virulent  strain  that  are  handed  from  one  person  to 
another  until  the  disease  sweeps  the  community.  Most 
of  us  must  either  endure  these  colds  or  find  a  way  to 
escape  the  germs  that  cause  them  —  no  easy  thing  to  do 
when  people  who  have  colds  insist  on  shaking  hands 
with  us  and  leaving  with  us  a  few  millions  of  the  germs 
with  which  they  are  so  bountifully  supplied. 

Spraying  the  nose  with  something  that  will  kill  the 
germs  often  helps  to  check  a  cold  in  its  early  stages. 

1  A  case  of  adenoids  has  been  reported  in  a  child  six  weeks  old  and 
one  in  a  man  of  seventy  years.  They  are  by  no  means  to  be  thought  of  as 
a  disease  of  children  only,  for  many  cases  are  found  in  persons  up  to  forty 
years  of  age. 


ADENOIDS  AND   COLDS  77 

A  hot  foot  bath  cannot  kill  the  germs  in  the  nasal  pas- 
sages, but  it  helps  to  draw  the  blood  away  from  the 
congested  parts  and  assists  in  correcting  the  disturbances 
of  the  circulation  that  accompany  a  cold.  It  may  also 
relieve  to  some  extent  the  headache  from  which  the 
victim  of  a  violent  cold  suffers.  A  hot  bath  taken  be- 
fore going  to  bed  is  even  better  than  a  foot  bath  for 
drawing  the  blood  away  from  the  congested  parts. 

In  chronic  colds,  the  germs  remain  with  the  person 
all  the  time,  growing  only  a  little  when  he  is  in  good 
health  and  offers  a  vigorous  resistance  to  them,  and 
springing  into  greater  activity  whenever  the  person  gets 
his  feet  wet,  becomes  chilled,  loses  sleep,  or  does  any- 
thing else  that  weakens  his  body  and  lowers  its  resist- 
ance to  germs.  A  person  with  a  cold  of  this  kind  is 
like  a  country  invaded,  but  not  conquered,  by  an  enemy. 
At  one  time  the  inhabitants  of  the  country  drive  back 
the  foe  and  give  themselves  a  breathing  spell ;  at  an- 
other time  the  advantage  is  with  those  who  make  the 
attack.  The  patient's  only  hope  of  victory  over  his  germ 
enemies  is  to  build  up  his  health  until  his  body  has  suf- 
ficient fighting  powers  to  drive  them  out  completely. 
The  following  practices  have  been  found  important  in 
giving  the  body  strength  for  this  work  :  — 

Clearing  out  the  nose  and  throat.  Adenoids,  enlarged 
tonsils,  bent  and  enlarged  bones  in  the  nose,  and  any- 
thing else  that  prevents  a  free  passage  of  the  air  through 
the  nose  and  a  free  drainage  of  the  mucus  from  it,  turn 
the  nasal  chambers  into  splendid  homes  for  countless 
germs.  The  battle  against  colds  is  a  battle  against 
germs,  and  we  cannot  hope  to  succeed  if  the  enemy  is 
intrenched  behind  fortifications. 


78  PRIMER   OF  PHYSIOLOGY 

Getting  enough  fresh  air.  Experience  with  both 
consumptives  and  well  persons  shows  that  no  one  thing 
is  so  important  as  fresh  air  in  giving  the  body  the 
power  to  kill  germs.  Many  persons  suffer  continually 
from  colds  because  they  live  and  work  in  buildings 
where  the  air  is  dry  and  overheated,  and  any  one  who 
wishes  to  free  himself  from  a  chronic  cold  must  include 
fresh  air  in  his  plans. 

Keeping  the  bowels  open.  When  refuse  matter  does 
not  pass  promptly  through  the  intestines,  it  putrefies 
and  produces  poisons  that  break  down  the  health  of  the 
whole  body  (pages  177-179).  These  poisons  destroy 
the  power  of  the  body  to  resist  germs,  and  they  injure 
the  nervous  system  so  that  the  blood  vessels  are  not  prop- 
erly controlled.  The  feet  of  persons  who  are  in  this 
condition  are  therefore  often  cold  while  other  parts  of 
the  body  are  congested  with  blood,  and  the  circulation 
in  general  is  not  regulated  as  it  should  be.  This  disturb- 
ance of  the  circulation  is  in  itself  favorable  to  the 
growth  of  germs  and  makes  the  cure  of  a  cold  difficult. 
The  remedy  is  to  get  the  digestive  system  into  good 
working  order,  and  many  persons  recover  from  chronic 
colds  when  they  do  this  (page  170). 

Taking  cold  baths.  The  practice  of  taking  cold 
baths  helps  to  give  freedom  from  colds.  Probably  one 
way  that  it  does  this  is  by  bringing  out  the  white  blood 
corpuscles  that  kill  germs;  for  it  is  found  that  the 
white  corpuscles  are  more  abundant  in  the  blood  after 
a  cold  bath  than  before  it.  Another  way  that  a  cold 
bath  helps  is  by  teaching  the  blood  vessels  in  the  skin 
to  open  and  close  promptly.  When  cold  strikes  the 
body,  these  vessels  ought  to  close  and  thus  keep  the 


ADENOIDS  AND   COLDS  79 

blood  in  the  inner  parts  where  the  heat  of  the  body  will 
not  be  lost.  Then,  when  the  cold  is  removed  from  the 
skin,  the  vessels  ought  to  open  and  allow  the  blood  to 
come  to  the  surface  ofNthe  body.  In  some  persons  who 
are  in  bad  health,  the  nervous  system  which  governs 
these  vessels  does  not  control  them  properly,  and  the 
vessels  in  the  skin  may  not  close  promptly  enough  to 
prevent  the  escape  of  the  heat  from  the  body;  or,  at 
the  slightest  feeling  of  cold  on  the  skin,  the  blood  vessels 
may  shut  up  tight  and  gorge  the  inner  parts  of  the  body 
with  hot  blood,  while  the  skin  is  left  cold  and  shivering.1 
Cold  baths  help  to  train  the  vessels  of  the  skin  to 
open  and  close  properly,  and  to  keep  the  right  amount 
of  heat  within  the  body.  In  beginning  to  take  baths  of 
this  kind,  intelligence  and  care  are  necessary  ;  otherwise 
much  harm  may  be  done  (page  88). 

Drafts  and  colds.  People  are  sometimes  advised  to 
pay  no  attention  to  drafts  and  to  open  the  windows, 
no  matter  how  cold  the  weather  may  be,  because  it  is 
germs  and  not  drafts  that  cause  colds.  Yet  many 
persons  know  from  their  own,  experience  that  sitting  in 
a  cold  draft  does  cause  them  to  sneeze,  to  feel  chilly, 
and  often  to  become  actually  sick.  How  can  the  idea 
that  it  is  beneficial  to  the  health  to  sleep  where  the 
wind  will  blow  over  you,  be  reconciled  with  the  idea 
that  a  draft  of  cold  air  is  dangerous  ?  If  motion  in  the 
air  is  desirable,  why  not  have  as  much  of  it  as  possible  ? 

1  It  should  be  understood  that  in  chills,  such  as  we  have  in  malaria,  or 
at  the  onset  of  grip  or  pneumonia,  the  difficulty  is  that  the  blood  has  been 
driven  to  the  inner  parts  of  the  body,  and  the  skin,  where  our  sense  of 
feeling  is,  no  longer  is  warmed  by  the  blood  flowing  through  it.  There  is 
no  lack  of  heat  in  the  body,  for  often  a  person  has  several  degrees  of  fever 
at  the  same  time  that  he  is  having  a  chill. 

X 


80  PRIMER   OF  PHYSIOLOGY 

In  the  first  place,  it  must  be  understood  that  drafts  of 
cold  air  take  the  heat  out  of  the  skin,  and  that  a  person 
who  is-  exposed  to  them  should  have  sufficient  extra 
clothing  to  enable  him  to  keep  up  his  body  heat.  This 
keeping  up  of  the  body  temperature  is  fundamental  in 
the  preservation  of  the  health,  for  the  resistance  of  the 
body  to  germs  is  weakened  at  once  by  the  loss  of  too 
much  heat.  Much  damage  may  be  done  by  compelling 
school  children  who  have  been  accustomed  to  hot  rooms 
to  sit  in  their  ordinary  clothing  with  the  windows  wide 
open  on  a  cold  day. 

In  the  second  place,  it  must  be  recognized  that  persons 
who  have  chronic  colds  —  those  who  are  carrying  a 
host  of  germs  just  ready  to  break  through  their  resist- 
ance and  put  them  to  bed  —  are  already  sick.  It  must 
also  be  recognized  that  what  is  safe  for  a  well  person 
or  for  one  accustomed  to  it,  may  be  neither  safe  nor 
wise  for  a  sick  person  or  for  one  not  accustomed  to  it. 
When  cold  air  strikes  a  person  who  is  in  a  half-sick 
condition,  the  vessels  in  the  skin  close  more  than  they 
should.  The  result  is  that  the  blood  is  driven  inward, 
so  that  in  a  few  minutes  the  person  can  feel  the  mucous 
membrane  in  his  nose  swelling  from  the  great  supply 
of  blood  in  it.  This  gorging  of  the  membrane  of  the 
nose  with  blood  causes  a  great  quantity  of  lymph  to 
escape  among  the  cells,  and  it  weakens  the  resistance 
of  the  mucous  membrane  so  that  the  germs  on  it  multiply 
more  rapidly. 

Cold  drafts  may  thus  cause  a  cold  in  a  person  who 
is  in  ill  health  by  disturbing  the  circulation  and  the  dis- 
tribution of  the  blood  ;  or  perhaps  it  is  better  to  say  that 
cold  drafts  make  a  chronic  cold  worse  in  this  way.  It 


ADENOIDS  AND   COLDS  8 1 

is  not  advisable,  therefore,  for  a  person  who  is  weak  or 
half-sick  to  expose  himself  suddenly  to  severe  conditions. 

Training  the  body  to  endure  ordinary  exposure.  A 
person  who  suffers  from  chronic  colds  needs  to  build  up 
the  strength  of  the  body  gradually;  to  accustom  the 
vessels  of  the  skin  to  cold  baths  gradually  so  that  they 
will  act  properly  instead  of  throwing  him  into  a  chill 
when  a  blast  of  cold  air  is  felt ;  to  clear  the  nasal  passages 
and  trie  throat  of  obstructions ;  to  stop  the  poisoning  of 
the  body  by  decaying  intestinal  wastes  ;  and,  in  general, 
by  degrees  to  bring  the  body  back  to  where  it  will  be 
able  to  stand  ordinary  exposure  without  injury  and  to 
kill  the  germs  that  are  causing  the  cold.  Any  one 
who  is  always  having  colds  ought,  therefore,  to  begin 
to  build  up  his  health,  and  if  he  is  wise  he  will  get  a 
good  physician  to  guide  him  in  this  task. 

Catarrh  and  bronchitis.  Catarrh  is  a  chronic  cold 
in  the  head.  Bronchitis  is  a  chronic  cold  in  the  bron- 
chial tubes.  In  both  cases  the  body  is  kept  poisoned 
by  the  germs  that  are  growing  in  it.  Recently  it  has 
been  discovered  that  in  most  cases  of  these  diseases,  the 
germs  spread  from  permanent  breeding  places  in  the 
tonsils  or  the  nasal  sinuses,1  and  that  treatment  is  use- 
less until  the  homes  of  the  germs  are  broken  up. 
There  is  often  no  swelling  or  pain  in  the  infected  parts, 
and  many  persons  who  are  greatly  in  need  of  medical 
attention  go  for  years  without  it.  Since  infections  of 
these  kinds  are  believed  to  cause  many  cases  of  rheuma- 
tism, heart  and  kidney  disease,  and  other  serious  ail- 
ments, they  should  be  given  prompt  medical  care. 

1The  nasal  sinuses  are  cavities  in  the  bones  that  open  off  from  the 
'chambers  of  the  nose. 


82  PRIMER  OF  PHYSIOLOGY 

QUESTIONS 

Describe  the  nasal  passages.  What  effect  has  the  mucous 
membrane  upon  the  air  that  passes  over  it  ?  Name  three 
troubles  that  may  occur  in  the  nose,  and  the  remedy  for 
them.  Describe  the  throat.  What  is  the  soft  palate?  What 
and  where  are  the  Eustachian  tubes? 

How  many  tonsils  are  there?  Where  are  they?  Of  what 
kind  of  tissue  are  the  tonsils  composed?  What  is  the  cause 
of  tonsillitis  ?  What  are  adenoid  growths? 

Give  five  symptoms  of  adenoids  that  show  in  the  face. 
Give  other  symptoms  and  effects  of  adenoids.  What  is  the 
remedy  for  adenoids  and  enlarged  tonsils  ?  Mention  some  bad 
effects  of  allowing  children  to  wait  to  outgrow  adenoids. 

By  what  are  colds  caused  ?  Distinguish  between  epidemic 
and  chronic  colds.  Give  three  ways  by  which  the  body  resist- 
ance to  the  germs  of  colds  may  be  raised.  How  does  the 
practice  of  taking  cold  baths  protect  one  from  colds?  Explain 
how  a  cold  draft  may  be  injurious.  What  should  a  person  who 
has  chronic  colds_do  to  bring  his  body  back  into  normal  con- 
dition ? 

What  is  catarrh?  What  is  bronchitis?  What  bad  effects 
have  they  upon  the  body  ? 

SUGGESTIONS  TO  THE  TEACHER 

In  every  school  that  is  without  medical  inspection  many  undis- 
covered cases  of  adenoids  and  enlarged  tonsils  may  be  found.  It  is 
a  simple  matter  to  learn  to  recognize  the  symptoms  of  these  troubles, 
and  the  teacher  can  do  no  greater  service  than  to  call  the  attention 
of  parents  to  the  children  who  are  suffering  from  them.  Among  the 
arguments  that  may  be  advanced  in  asking  that  the  afflicted  children 
be  given  medical  attention  are  : 

The  wasting  of  the  school  opportunities  of  the  child ;  the  fixing 
for  life  of  habits  of  idleness ;  the  danger  of  injury  to  the  hearing ; 
the  permanent  catarrhal  effects  ;  and  the  marring  of  the  regularity  of 
the  teeth  and  the  beauty  and  symmetry  of  the  face. 


CHAPTER    NINE 

CLOTHING  AND   THE  BODY  HEAT 


FIGS.  74  and  75.    The  object  of  clothing  is  to  keep  up  the  body  heat. 

A  MAN  in  the  cold  arctics  loses  much  more  heat  than 
does  a  man  in  the  warm  tropics.  Yet  the  temperature 
of  the  human  body  all  over  the  world  is  the  same.  A 
man  who  is  exercising  violently  produces  five  or  six 
times  as  much  heat  as  a  resting  man  produces.  Yet  the 
temperature  of  the  human  body  during  exercise  and  rest 
is  practically  the  same.  Cold-blooded  animals  become 
warm  or  cold  according  to  the  temperature  of  their 
surroundings,  but  the  warm-blooded  animals,  including 
man,  keep  their  heat  near  a  certain  point  whether  the 
weather  is  hot  or  cold.  In  health  the  temperature  of 
the  human  body  varies  from  98.8  degrees  to  about  one 
and  one  half  degrees  below  this  point. 

The  object  of  clothing.  We  take  our  clothing  so  much 
as  a  matter  of  course,  that  we  often  forget  that  the  one 
great  purpose  in  wearing  it  is  to  protect  us  from  cold. 
It  is  true  that  it  protects  the  body  from  wounds  also,  and 
we  pay  great  attention  to  it  because  of  its  effect  on  our 
appearance ;  but  yet  the  fact  that  the  inhabitants  of  the 


84 


PRIMER   OF  PHYSIOLOGY 


hair 


epidermis 


touch 
corpuscle 


frigid  regions  are  clad  from  head  to  foot  in  furs,  while 
those  who  live  in  the  tropics  are  often  very  scantily  clad, 
shows  that  man  put  on  clothing,  just  as  he  built  houses, 
to  protect  himself  from  the  weather.  We  ought  not, 
therefore,  to  become  so  interested  in  the  colors  and  the 
appearance  of  our  clothing  that  we  forget  the  real 
reason  why  it  is  worn. 

The  necessity  for  a  regulator  of  the  body  heat.  To  a 
certain  extent  we  can  regulate  the  heat  of  the  body  by 
wearing  heavy  clothes  in  winter  and  lighter  clothing 

when  the  weather  is  hot. 
Yet  we  cannot  regulate 
the  loss  of  heat  from  the 
body  by  clothing  alone  ; 
for  the  temperature  of 
the  body  must  be  kept 
constantly  at  one  point, 
while  the  thermometer 
often  runs  up  and  down 
20  or  30  degrees  in  a 
single  day.  There  must, 
therefore,  be  some  deli- 
cate regulator  that  will 
govern  the  loss  of  heat 
from  the  body  according 
to  the  changes  in  the 
temperature  of  the  air. 
This  work  is  done  by 
the  skin. 
The  skin  is  composed  of  a 


dermis 


sweat   fat     ne 
gland 
A  section  of  the  skin. 


FIG.  76. 

The  structure  of  the  Skin, 
tough  outer  layer  called  the  epidermis,  and  of  a  deeper 
layer  of  connective  tissue  called  the  dermis.     The  outer 


CLOTHING  AND   THE  BODY  HEAT  85 

cells  of  the  epidermis  are  dead  and  are  continually 
scaling  off,  but  the  cells  in  the  lower  part  multiply 
and  grow  to  take  the  places  of  those  that  are  lost. 
The  dermis  contains  the  nerves  of  touch  and  great 
numbers  of  small  blood  vessels.  Below  the  dermis  is  a 
layer  of  loose  connective  tissue  in  which  a  considerable 
quantity  of  fat  is  stored.  This  layer  of  fat  helps  to 
retain  the  body  heat. 

Hair  follicles  and  sweat  glands.  At  certain  points  the 
epidermis  is  folded  down  into  deep  pockets  called  hair 
follicles,  from  the  bottom  of  which  the  hairs  grow.  At 
other  points  sweat  glands  run  down  from  the  outer  sur- 
face of  the  epidermis  and  lie  coiled  in  the  dermis.  The 
sweat  glands  are  hollow  tubes,  the  lower  ends  of  which 
are  surrounded  by  lymph.  Water  from  the  lymph  soaks 
through  the  walls  into  the  tubes  and  flows  out  of  the 
mouths  of  the  glands  as  sweat. 

The  body  heat  regulated  by  the  sweat  glands  and 
vessels  of  the  skin.  The  temperature  of  the  body  is 
regulated  by  the  sweat  glands  and  the  small  arteries 
of  the  skin.  During  hot  weather  and  when  we  do 
hard  work,  the  sweat  glands  assist  in  cooling  the  body 
by  pouring  out  sweat  on  the  surface  of  the  skin.  The 
evaporation  of  the  sweat  cools  the  skin,  just  as  alcohol 
cools  it  when  allowed  to  evaporate  from  it.  The  ar- 
teries do  their  part  of  this  work  by  controlling  the 
amount  of  blood  that  comes  into  the  skin.  When 
the  body  is  exposed  to  cold,  these  small  arteries 
contract  and  keep  the  blood  in  the  warm  inner  or- 
gans. When  the  body  is  heated,  they  relax  and  allow 
the  blood  to  come  to  the  surface,  where  it  will  be 
cooled. 


86  PRIMER   OF  PHYSIOLOGY 

The  danger  of  chilling  the  body.  Chilling  the  body 
disturbs  the  circulation  by  driving  the  blood  from  the 
skin  and  congesting  the  inner  parts  of  the  body.  This 
makes  us  especially  liable  to  be  attacked  by  the  germs  of 
pneumonia,  influenza,  and  colds,  —  all  of  them  germs  that 
are  often  in  the  air  passages  waiting  for  a  favorable  op- 
portunity to  set  up  their  growth.  Wet  footwear  takes 
the  heat  out  of  the  feet,  thus  causing  the  mucous 
membrane  of  the  air  passages  .and  lungs  to  be  gorged 
with  the  blood  that  ought  to  be  in  the  lower  limbs,  and 
interfering  with  the  germ-killing  function  of  the  white 
corpuscles.  The  wearing  of  rubbers  when  they  are 
needed  to  keep  the  feet  dry  is  a  most  important  precau- 
tion in  guarding  against  colds. 

Danger  of  overheating  the  body.  Working  in  a  hot, 
moist  atmosphere  is  very  exhausting,  and  it  is  almost 
impossible  to  keep  up  the  health  during  the  summer 
months  unless  we  can  have  air  currents  to  blow  away 
the  hot  air  from  about  the  body.  Often  these  can  be 
secured  by  sleeping  and  working  outdoors,  by  opening 
windows,  and  by  the  use  of  ventilators  and  electric  fans. 
Some  persons  do  not  yet  realize  that  from  the  standpoint 
of  health  it  is  as  important  to  keep  cool  in  summer  as 
to  keep  warm  in  winter.  Accordingly,  they  are  willing 
to  pay  large  sums  to  heat  the  rooms  in  which  they  live 
and  work  in  winter,  but  are  not  willing  to  spend  a  small 
sum  for  ventilators  and  electric  fans  to  be  used  during 
the  heat  of  the  summer.  Just  as  being  chilled  in  winter 
makes  us  liable  to  attacks  of  influenza  and  pneumonia,  so 
overheating  in  summer  lowers  our  resistance  to  germs 
and  makes  us  liable  to  attacks  of  diarrhea,  dysentery, 
and  other  summer  diseases. 


CLOTHING   AND    THE  BODY  HEAT 


Suiting  the  clothing  to  the  weather.  Men  who  are 
brought  into  hospitals  suffering  with  sunstroke  are  often 
found  to  be  wearing  heavy 
coats  and  undershirts,  and 
thick  woolen  trousers.  Little 
babies  in  hot  summer  weather 
are  often  covered  with  "nettle 
rash"  and  "  heat  rash,"  be- 
cause they  are  dressed  in  such 
heavy  clothing  that  the  skin  is 
kept  in  an  overheated  condi- 
tion. On  the  other  hand,  we 
often  see  people  going  without 
wraps  and  overcoats  when 
the  weather  is  so  cold  that 
the  body  heat  can  scarcely 
be  kept  up  with  the  heaviest 
clothing.  What  we  need  to 
remember  is  that  the  object 
of  dress  is  to  keep  the  proper 
amount  of  heat  in  the  body. 
In  the  spring  and  fall,  especially  when  the  weather 
is  changeable,  it  is  important  that  the  weight  of  the 
clothing  correspond  to  the  needs  of  the  body. 

Bathing.  One  object  of  bathing  is  to  cleanse  the 
body.  This  we  need  not  discuss.  Bathing  as  it  relates 
to  health  is  mainly  a  question  of  the  temperature  of  the 
water.  Cold  baths  educate  the  vessels  of  the  skin  so 
that  they  learn  to  open  and  close  quickly  and  thus  regu- 
late the  body  heat  properly.  The  importance  of 
having  the  blood  vessels  trained  to  do  this  is  better 
appreciated  when  we  remember  that  animals  in  the 


FIG.  77.  A  Filipina  wearing  a 
costume  that  is  attractive  and  well 
suited  to  a  warm  climate.  The 
material  of  which  the  clothing  is 
made  is  thin,  and  the  large  sleeves 
and  open  neck  allow  the  heated  air 
to  escape  from  around  the  body. 


88  PRIMER   OF  PHYSIOLOGY 

natural  state  must  adapt  themselves  only  to  changes  in 
the  weather,  while  man  often  passes  in  a  few  seconds 
from  an  artificially  heated  building  into  an  outdoor  at- 
mosphere that  is  30  or  40  degrees  colder.  When  these 
quick  changes  from  warm  to  cold  air  are  made,  the  ves- 
sels ought  to  contract  promptly  and  shut  the  blood  off 
from  the  skin  before  too  much  heat  is  lost  from  the  body. 

The  training  of  the  blood  vessels  through  cold  baths 
is  of  course  mainly  a  work  of  training  the  nervous  sys- 
tem which  controls  the  vessels,  and  if  a  person  is  weak 
and  out  of  condition,  a  cold  bath  may  have  about  the 
same  effect  on  his  nervous  system  that  a  long  race 
would  have  on  the  muscles  of  a  person  not  accustomed 
to  taking  exercise.  In  beginning  to  take  cold  baths, 
therefore,  we  must  use  care.  They  ought  to  be  begun 
with  water  that  is  only  cool,  the  bath  should  be  short, 
and  after  the  bath  the  skin  should  be  rubbed  briskly 
with  a  rough  towel.  Colder  water  may  be  used  as  the 
skin  becomes  accustomed  to  it,  but  in  no  case  should 
the  water  be  so  cold  or  the  bath  so  prolonged  that  the 
reaction  fails  to  come  promptly;  for  when  this  is  the 
case,  the  blood  congests  the  inner  organs  and  a  head- 
ache is  the  usual  result. 

It  is  the  opinion  of  some  physicians  that  certain 
delicate  persons  are  never  able  to  take  cold  baths 
without  injury ;  that  baths  of  this  kind  are  injurious 
to  any  one  who  is  in  poor  health  or  in  a  nervous  con- 
dition, and  that  only  those  who  are  strong  and  in 
robust  health  can  bear  the  shock  of  such  a  bath  with- 
out injury.  Others  think  that  any  one  can  train  him- 
self to  take  them  with  safety.  This  question  we  must 
leave  to  the  physicians  to  decide. 


CLOTHING  AND   THE  BODY  HEAT 


89 


Alcohol  and  the  body  heat.  In  cold  weather,  taking 
alcohol  causes  a  feeling  of  warmth,  and  men  often  take  a 
drink  to  enable  them  better  to  endure  cold.  The  feeling 
of  warmth  that  is  given  by  alcohol  is  deceptive.  We 
feel  cold  when  the  blood  has  been  shut  off  from  the 
skin  and  warm  when  the  hot  blood  from  the  inner  parts 


FIG.  78.  Captain  Roald  Amundsen,  who  discovered  the  South  Pole.  Because 
alcohol  lessens  both  the  endurance  of  the  muscles  and  the  power  of  the  body 
to  resist  cold,  none  of  it  was  used  on  the  Amundsen  expedition. 

of  the  body  is  flowing  through  the  skin.  Alcohol 
temporarily  paralyzes  the  arteries  of  the  skin  and  leaves 
them  expanded.  This  allows  the  skin  to  become  flushed 
with  blood,  and  causes  a  sensation  of  warmth,  but  at  the 
same  time  it  allows  the  blood  to  be  cooled  and  the  body 
heat  to  be  lost.  When  we  are  exposed  to  cold,  the 
vessels  ought  to  be  contracted  and  we  ought  to  feel 
cold.  Hence  to  bring  the  blood  into  the  skin  so  that 
the  body  heat  will  be  lost  is  an  unnatural  and  unsafe 
thing  to  do.  Persons  who  use  alcohol  cannot  endure 
cold  so  well  as  persons  who  do  not  use  it,  as  the  ex- 
perience of  polar  explorers  proves. 


90  PRIMER   OF  PHYSIOLOGY 


QUESTIONS 

What  is  the  temperature  of  the  body?  What  is  the  purpose 
of  clothing?  Why  must  the  body  have  some  means  of  regu- 
lating its  heat? 

Name  the  two  layers  of  the  skin.  Describe  each.  Describe 
a  hair  follicle.  Describe  a  sweat  gland.  What  is  the  source 
of  the  sweat  ? 

Explain  how  the  heat  of  the  body  is  regulated.  In  what 
two  ways  does  chilling  the  body  injure  it?  How  may  wet  feet 
injure  the  health? 

What  is  the  effect  upon  the  health  of  overheating  the  body  ? 
Why  are  air  currents  especially  important  in  summer?  How 
may  they  be  secured?  Discuss  the  subject  of  suiting  the 
clothing  to  the  weather.  At  what  seasons  of  the  year  should 
we  be  especially  careful  to  change  clothing  according  to  the 
weather  ? 

What  do  cold  baths  do  for  the  vessels  of  the  skin  ?  How 
should  one  unaccustomed  to  cold  baths  begin  to  take  them  ? 

Why  does  taking  alcohol  give  a  sensation,  of  warmth? 
What  has.  been  the  experience  of  polar  explorers  in  regard  to 
the  power  of  drinkers  and  of  abstainers  to  withstand  cold  ? 

SUGGESTIONS   TO  THE  TEACHER 

Have  the  pupils  explain  why  an  athlete  throws  a  sweater  over  his 
shoulders  when  the  game  stops  for  a  few  minutes.  Insist  that  cloth- 
ing should  be  adapted  to  the  weather  and  not  to  the  season. 

Bring  out  the  difference  between  cold-blooded  and  warm-blooded 
animals  and  point  out  that  practically  all  warm-blooded  animals  are 
protected  by  feathers  or  by  hair. 


CHAPTER   TEN 

THE   NERVOUS   SYSTEM 

THE  work  of  the  nervous  system  has  always  been  a 
mystery  to  mankind.  The  ancient  Greeks  thought  that 
the  brain  distilled 
some  kind  of  vital 
spirit,  or  essence, 
which  flowed  out 
through  the  body  in 
the  form  of  a  gas. 
If  the  brain  were  in- 
jured so  that  the 
supply  of  this  spirit 
was  cut  off,  or  if  the 
body  were  deeply 
wounded  so  that  the 
vital  spirit  escaped, 
life  came  to  an  end. 

Today  we  know  a 
great  deal  more  than 
the  Greeks  knew 
about  the  nervous 
system,  but  our 
knowledge  of  it  is  yet 
far  from  complete. 
We  know  enough, 
however,  to  help  us 
greatly  in  the  care 

Of   the    body,    and    in  FlG'  79'    The  nervous  system. 

this  chapter  we  shall  take  up  some  of  the  facts  concern- 
ing the  nervous  system  that  it  is  most  important  for  us 
to  understand. 

91 


92  PRIMER   OF  PHYSIOLOGY 

The  parts  of  the  nervous  system.  "The  nervous  sys- 
tem is  composed  mainly  of  the  brain,  the  spinal  cord, 
and  forty-three  pairs  of  nerves  that  run  out  from  the 
brain  and  the  spinal  cord  to  all  parts  of  the  body. 
It  includes  also  many  little  masses  of  gray  tissue,  called 
ganglia  (singular,  ganglion),  that  are  found  among  the 
inner  organs  of  the  body,  and  a  great  network  of  nerve 
fibers  that  run  among  these  organs. 

The  function  of  the  nervous  system.  The  first  func- 
tion of  the  nervous  system  is  to  control  all  the  organs  and 
parts  of  the  body.  If  the  heart  should  beat  fast  when 
we  lie  down  to  rest  and  slow  when  we  run ;  if  the  sweat 
glands  should  pour  out  water  on  the  skin  when  we  are 
already  freezing  and  stop  work  on  the  hot  days  of  sum- 
mer; if  the  muscles  moved  how  and  when  they 
pleased,  so  that  they  jerked  the  body  aimlessly  about; 
if  all  the  organs  worked  without  system  or  plan,  so  that 
each  part  of  the  body  carried  on  its  activities  without 
regard  to  the  rest  of  the  body,  we  should  not  have  a 
working  machine  at  all,  but  only  a  collection  of  organs 
and  parts.  A  ruler  must,  therefore,  be  set  over  the 
whole  body  to  keep  all  the  parts  working  together 
properly.  This  ruler  is  the  nervous  system. 

The  second  function  of  the  nervous  system  is  to  act  as 
the  organ  of  the  mind.  This  function  we  shall  discuss 
when  we  take  up  the  study  of  the  brain. 

The  nervous  system  composed  of  cells  and  fibers.  The 
nervous  system  is  made  up  of  nerve  cells  and  of  nerve 
fibers.  The  nerve  cells  are  larger  than  most  of  the  body 
cells,  and  have  a  gray  color.  Most  of  the  nerve  cells  are 
found  in  the  brain  and  spinal  cord,  but  a  few  of  them  are 
found  in  the  ganglia,  which  are  little  balls  of  nerve  cells. 


THE  NERVOUS  SYSTEM  93 

The  nerve  fibers  connect  the  nerve  cells  with  the 
other  parts  of  the  body.  They  have  a  glistening  white 
color,  but  each  fiber  has  a  gray  central  part  which 
carries  messages  to  and  from  the  spinal  cord  and 
brain.  This  gray  core  of  the  fiber  is  a 
branch  of  a  nerve  cell,  and  we  may 
think  of  the  nerve  fibers  as  long 
branches  of  the  cells  which  run  out  to 
all  parts  of  the  body.  The  white  nerves 
that  we  see  in  the  body  of  an  animal 
are  bundles  of  nerve  fibers.  The  finest 
nerves  contain  but  a  few  fibers,  and  can 
be  seen  only  with  a  microscope.  The 
sciatic  nerve,  which  runs  to  the  leg,  is 
the  largest  nerve  in  the  human  body. 
This  is  a  flattened  cord  three  fourths  of 
an  inch  across. 

Motor  and  sensory  nerve  fibers. 
Some  of  the  nerve  fibers  carry  mes- 
sages from  the  brain  and  spinal  cord 
that  cause  our  muscles  to  move.  These  FlG-  8o-  A  nerve  ceil 

,,     ,  ~,  s-\  i          fi  and  nerve  fiber.  At  the 

are  called  motor  fibers.     Other  fibers  lower  end  the  attach. 
carry  messages  from  the  skin,  the  eye,  ment  of  the  fiber  *> the 

. ,  j      ,  i  r  , ,       ,       i  muscle  cells  is  shown. 

the  ear,  and  other  parts  of  the  body  to 
the  brain.  These  messages  cause  us  to  feel,  to  see,  to 
hear,  and  to  understand  the  condition  of  all  the  parts 
of  the  body.  They  cause  sensations  in  the  brain,  and 
the  fibers  over  which  they  pass  to  reach  the  brain  are 
called  sensory  fibers. 

The  brain.  The  brain  is  a  mass  of  very  soft  tissue 
weighing  about  fifty  ounces  and  filling  the  cavity  of  the 
cranium  (Fig.  21).  It  has  three  principal  divisions,  the 


94  PRIMER    OF  PHYSIOLOGY 

cerebrum,  the  cerebellum,  and  the  medulla  oblongata. 
A  general  idea  of  the  appearance  of  the  different  parts 
of  the  brain  may  be  gained  from  Figure  81. 

conwlutions 


medulla  oblongata    ^IP'      cerebellum 
FlG.  81.    The  brain  seen  from  the  side,  showing  the  three  principal  divisions. 

The  cerebrum.  The  cerebrum  makes  up  more  than 
three  fourths  of  the  entire  brain.  It  is  divided  by  a  deep 
groove  into  right  and  left  hemispheres.  The  outside 
layer  of  the  cerebrum  is  composed  of  nerve  cells,  and 
therefore  has  a  gray  color.  To  make  more  room  for 
these  cells  the  whole  surface  of  the  cerebrum  is  thrown 
into  folds,  or  wrinkles,  that  are  called  convolutions. 

From  the  cells  of  the  cerebrum  a  great  network  of 
fibers  runs  in  all  directions  through  the  brain,  and 
connects  all  its  different  parts  with  each  other.  Other 
fibers  run  down  through  the  medulla  into  the  spinal 
cord  and  connect  the  cerebrum  with  all  parts  of  the 
body.  Most  of  the  motor  fibers  from  the  cerebrum  are 
crossed  in  the  medulla,  so  that  the  right  side  of  the 
cerebrum  is  connected  with  the  muscles  of  the  left  side 
of  the  body,  and  the  left  side  of  the  cerebrum  is  con- 
nected with  the  muscles  of  the  right  side  of  the  body. 

The  function  of  the  cerebrum.  The  gray  outer  layer 
of  the  cerebrum  is  the  seat  of  all  intelligence.  Without 


THE  NERVOUS  SYSTEM 


95 


it  all  sensations  of  light,  sound,  taste,  smell,  touch,  heat, 
and  hunger  are  lost.  When  it  is  removed,  all  power  of 
moving  the  voluntary  muscles  is  gone.  The  cerebrum, 
therefore,  is  the  part  of  the  brain  that  thinks  and  feels. 
It  is  the  part  that  causes  us  to  remember  and  to  know,  to 
love  and  to  hate,  to  be  glad  and  to  be  sad.  The  cere- 
brum decides  what  we  shall  do ;  it  sends  out  the  mes- 
sages to  the  muscles  when  we  wish  to  move;  and  it 
governs  the  whole  body.  With- 
out its  cerebrum  an  animal  can 
live,  but  all  its  intelligence  is 
gone.  It  still  breathes  and  its 
heart  continues  to  beat,  but  it  is 
only  a  machine,  knowing  nothing 
of  its  own  needs  and  of  the 
world  about  it. 

The  cerebellum.  The  cerebel- 
lum lies  under  the  back  lobes  of 
the  cerebrum.  Its  function  is  to  FlG  82 

Cause  all  the  muscles  to  keep   the    from  above,  showing  the  hemi- 

proper  tension,  and  to  assist  in 

governing  the  muscles  of  locomotion.  In  walking,  more 
than  two  hundred  muscles  are  used  in  holding  the  body 
upright  and  in  moving  the  different  parts  that  are  brought 
into  action.  Each  of  these  muscles  must  contract 
with  exactly  the  right  force  and  at  exactly  the  right  time, 
or  they  will  work  against  each  other  and  the  right 
movements  will  not  be  made.  When  the  cerebellum  is 
injured,  all  the  muscles  are  weakened  and  relaxed,  and 
the  person  loses  control  of  the  muscles  that  support  the 
body  and  move  the  legs.  This  causes  him  to  stagger 
and  reel  like  a  drunken  man. 


cerebrum  seen 


96  PRIMER   OF  PHYSIOLOGY 

The  medulla  and  the  spinal  cord.  The  spinal  cord  is 
about  half  an  inch  in  diameter  and  eighteen  inches  long. 
Without  the  roots  of  the  nerves  that  rise  from  it,  it 
weighs  about  an  ounce.  It  lies  in  the  canal  in  the  center 
of  the  spinal  column  and  is  securely  protected  by  the 
bones  about  it.  The  enlarged  upper  end  of  the  cord 
is  the  medulla. 

Both  the  spinal  cord  and  the  medulla  are  composed 
in  large  part  of  fibers  that  connect  the  brain  with  the 
different  body  parts.  Some  of  these  are  sensory  fibers, 
through  which  messages  from  the  body  are  passed  up 
to  the  brain.  Others  are  motor  fibers,  over  which 
commands  from  the  brain  pass  down  on  their  way  to 
the  different  parts  of  the  body.  In  addition,  the  medulla 
contains  the  centers  which  govern  the  heart  and  lungs. 
When  the  cerebrum  of  an  animal  is  removed,  the  intel- 
ligence is  lost;  when  the  cerebellum  is  injured,  control 
of  the  muscles  is  lost;  but  when  the  medulla  is  injured, 
life  at  once  ceases,  because  the  beating  of  the  heart 
and  the  breathing  stop. 

Reflex  action.  Much  of  the  governing  of  the  body 
by  the  nervous  system  is  done  without  thought.  The 
messages,  or  nerve  impulses,  pass  through  the  sensory 
nerve  fibers  into  the  nerve  cells,  pass  on  through  the 
branches  of  these  cells  into  other  cells  that  are  touching 
them,  and  come  out  again  by  way  of  a  motor  nerve. 
An  action  that  is  caused  in  this  way  is  called  a  reflex 
action,  and  it  can  best  be  explained  by  an  example. 

Cross  your  legs,  and  strike  yourself  just  below  the 
kneecap  with  the  edge  of  your  hand.  If  you  strike  the 
right  place,  you  will  start  messages  to  the  spinal  cord. 
These,  without  any  thought  whatsoever  on  your  part,  will 


THE  NERVOUS  SYSTEM 


97 


pass  into  the  motor  nerves  and  down  into  the  muscles  of 

the  leg.     The  muscles  of  the  leg  will  then  contract  and 

cause  the  foot  to  jerk.    A  reflex  action  is  an  involuntary 

action  caused  by  an  impulse  that 

starts  in  a  sensory  nerve.     It  is 

very  different  from  the  voluntary 

actions  that  are  caused  by  im- 

pulses which  start  in  the  cere- 

brum and  pass  out  to  the  muscles 

when  we  wish  to  move  some  part 

of  the  body.     Practically  all  the 

governing  of  the  internal  organs 

of  the  body  is  carried  on  by  re- 

flexes. 

Reflexes  acquired  through 
practice.  The  reflexes  that  we 
have  been  discussing  are  natural 

a  i  •   i    ..  i 

reflexes  ;  we  are  born  with  them. 

There    is  another  Set  of  reflexes 

that  comes  to  us  through  prac- 

tice.       The  Skilled  Swimmer  does 

not  think  how  he  shall  move  his 
arms  and  legs  ;  in  boxing,  the  hands  move  without 
thought  and  almost  faster  than  the  eye  can  follow; 
the  telegrapher  does  not  think  about  the  combination 
of  dots  and  dashes  that  spell  out  a  word,  but  reads 
the  message  he  is  sending,  and  his  hand  does  the  rest. 
In  the  same  way,  all  of  us  every  day  do  a  great  part 
of  our  work  without  thought.  We  walk  without  giving 
attention  to  the  muscles  and  parts  which  we  must 
move  ;  we  open  our  mouths  to  take  in  food  without 
thinking  ;  we  chew  our  food  without  noticing  that  we 


FlG<  83>   The  ball  starts  from 
the  hand  and  comes  back  to  it 

again.  The  impulse  that  causes 

asreflex  actionpstarts  from  the 

outer  end  of  a  sensory  nerve 


action.    //  does  not  start  from 

the  brain' 


98  PRIMER   OF  PHYSIOLOGY 

are  chewing ;  we  write  without  conscious  thought  as 
to  the  shape  of  the  letters.  All  these  things  we 
have  repeated  so  often  that  we  have  learned  to  do 
them  without  thought. 

Acquired  reflexes  and  education.  A  very  important 
part  of  education  consists  in  establishing  the  right  re- 
flexes, so  that  without  thought  we  shall  do  the  more 
common  things  of  life  properly.  A  young  person  who 
is  learning  to  write  ought  to  learn  to  hold  his  pen  in  the 
right  way  and  to  shape  the  letters  correctly,  so  that  the 
right  reflexes  will  be  formed  and  the  writing  question 
settled  for  life.  He  ought  to  learn  to  group  his  words 
properly  and  to  give  the  right  inflection  in  reading,  so 
that  these  matters  will  attend  to  themselves  thereafter. 
He  ought  to  take  great  care  to  say  "  please  "  and  "  thank 
you  " ;  to  modulate  his  voice  so  that  it  will  not  become 
loud  and  strident  when  he  is  talking  eagerly ;  to  take 
off  his  hat  and  to  rise  to  his  feet  when  he  should  do 
so;  'and  to  do  all  the  other  things  that  go  to  make 
up  pleasant  manners;  for  no  one  will  ever  have  good 
manners  who  has  not  established  reflexes  that  will  make 
him  able  to  do  what  he  ought  to  do  naturally  and  with- 
out thought  of  his  actions. 

When  you  are  learning  to  do  anything,  the  great 
thing  is  to  do  it  right,  so  that  you  will  form  a  reflex 
action  of  the  right  kind.  Then  as  long  as  you  live 
the  part  of  your  conduct  and  work  that  depends  on 
this  reflex  will  take  care  of  itself  and  you  will  be 
free  to  expend  your  energy  on  the  new  problems  that 
arise  day  by  day.  The  object  of  the  training  that 
you  are  receiving  at  home  and  in  school  is  to  make 
for  you  a  set  of  tools  with  which  to  carry  on  the  work 


THE  NERVOUS  SYSTEM  99 

of  your  life.  If  you  wish  to  be  a  good  workman,  you 
must,  first  of  all,  manufacture  for  yourself  a  good  set 
of  tools. 

Habits.  Habits  are  really  reflexes  that  we  form  by 
repeating  acts,  and  just  as  physical  habits  can  be  formed, 
so  can  moral  habits,  and  habits  of  the  mind,  be  formed. 
All  kinds  of  habits  are  formed  most  readily  in  youth, 
and  it  is  seldom  that  long-established  habits  are  broken 
after  the  age  of  twenty-five  or  thirty.  Indeed,  it  is  dif- 
ficult at  any  time  of  life  to  break  a  habit  that  has  once 
been  thoroughly  established.  It  is  because  this  is  true 
that  young  people  are  so  constantly  urged  to  form  habits 
of  honesty,  neatness,  accuracy,  and  cleanliness.  An 
investigation  at  Harvard  University  has  shown  that  the 
students  who  do  high-grade  work  in  the  schools  of  law, 
medicine,  and  engineering  are  students  who  did  their 
work  well  before  entering  these  schools ;  that  it  makes 
little  difference  what  subjects  they  have  studied  previ- 
ously, but  that  it  makes  a  great  deal  of  difference  whether 
they  have  formed  the  habit  of  learning  their  lessons 
regularly  and  thoroughly,  or  of  going  through  them  in  a 
lazy  and  careless  way.  The  trifler  in  the  lower  grades 
of  school  is  usually  a  trifler  still  in  the  high  school,  and 
very  few  high-school  drones  ever  become  capable  and 
industrious  college  students. 

Just  what  it  is  that  makes  the  nervous  system  want  to 
keep  on  doing  things  in  the  same  way,  we  shall  not 
attempt  to  explain,  but  it  is  a  well-known  fact  that  what 
a  man  does  in  youth  determines  very  largely  what  kind 
of  person  he  will  be  in  later  life.  If  in  youth  he  forms 
habits  of  dishonesty  and  laziness,  he  is  almost  certain 
to  develop  into  an  unreliable  and  unsuccessful  man. 


100  PRIMER   OF  PHYSIOLOGY 

If  in  youth  he  forms  habits  of  honesty,  industry,  and 
promptness,  he  will  probably  become  a  trusted  and  a 
successful  man.  Rip  Van  Winkle  was  always  intending 
to  stop  drinking,  but  when  a  glass  was  offered  him,  he 
would  say :  "  We  won't  count  this  time  "  ;  so  the  time  to 
begin  his  new  life  never  came.  There  are  many  persons 
who  have  good  intentions  and  are  meaning  to  get  down 
to  work  in  the  future,  but  their  habits  keep  them  loiter- 
ing on  in  the  same  old  ways.  The  importance,  therefore, 
of  forming  correct  habits  in  youth  can  hardly  be  over- 
estimated. 

QUESTIONS 

Name  the  principal  parts  of  the  nervous  system.     Give  two 
functions  of  the  nervous  system.   Of  what  is  the  nervous  system ' 
composed?   Describe  a  nerve  fiber.    What  are  ganglia?     What 
are  motor  nerve  fibers  ?  sensory  nerve  fibers  ? 

Describe  the  brain.  Describe  the  cerebrum.  How  is  the 
cerebrum  connected  with  the  other  parts  of  the  brain?  with  all 
the  parts  of  the  body?  What  is  the  function  of  the  cerebrum? 
What  part  of  the  cerebrum  is  the  seat  of  intelligence?  Can 
an  animal  live  if  its  cerebrum  is  removed? 

Where  is  the  cerebellum?  What  is  its  function?  What  effect 
upon  a  person  has  an  injury  to  the  cerebellum? 

Describe  the  spinal  cord  and  the  medulla.  Why  does  injury 
to  the  medulla  cause  death? 

What  is  a  reflex  action?  Give  an  example.  Describe  the 
course  of  the  impulse  in  a  reflex  action.  Describe  the  course 
of  the  impulse  in  a  voluntary  action.  What  is  an  acquired  re- 
flex? How  may  right  reflexes  be  established?  Why  is  it  im- 
portant to  establish  this  kind  of  reflexes  ? 

What  is  a  habit?  Why  is  it  so  important  to  establish,  right 
habits  in  youth?  What  did  the  investigation  at  Harvard 
University  show  in  regard  to  the  foundation  of  good  scholarship  ? 


THE  NERVOUS  SYSTEAf    •>•'.  \  •         IOI 


SUGGESTIONS  TO  THE  TEACHER 

Secure  if  possible  prepared  microscopic  mounts  that  will  show 
nerve  cells,  nerve  fibers,  and  the  cross-section  of  a  nerve,  and  have 
the  pupils  examine  them.  For  demonstrating  the  gross  structure 
of  the  brain,  the  brain  of  a  sheep  is  very  commonly  used.  If  a 
sheep's  head  is  not  easily  available,  the  head  of  a  cat,  rabbit,  or  fowl 
may  be  used.  A  pair  of  bone  forceps  will  be  needed  for  breaking 
away  the  skull,  and  after  removal  the  brain  should  be  hardened  in 
alcohol  or  five  per  cent  solution  of  formalin. 

Make  clear  that  a  reflex  action  is  always  involuntary^  but  may  or 
may  not  be  unconscious.  A  good  example  of  an  unconscious  reflex 
is  the  expansion  and  contraction  of  the  pupil  that  follows  shading 
the  eye  and  then  exposing  it  to  the  light.  With  the  aid  of  a  mirror 
the  pupil  can  observe  this  in  his  own  eye  by  facing  the  light,  cover- 
ing his  eye  with  his  hand,  and  then  removing  the  hand.  If  no 
mirror  is  at  hand,  the  experiment  may  easily  be  performed  on  an- 
other person.  To  a  great  extent  the  internal  organs  are  governed 
by  reflexes  of  this  class.  The  winking  or  dodging  reflex  may  be 
used  to  illustrate  conscious  reflexes. 

Emphasize  the  physical  aspects  of  habit.  Bring  out  the  fact  that 
in  the  doing  of  our  daily  work  and  the  living  of  our  daily  lives  it  is 
inevitable  that  we  shall  form  either  correct  habits  or  wrong  habits. 
The  late  Professor  James'  discussion  of  habit,  which  may  be  found 
in  either  his  7^alks  to  Teachers  or  his  Textbook  of  Psychology  (pub- 
lished by  Henry  Holt  and  Co.,  New  York),  is  a  masterly  and  inspir- 
ing piece  of  writing.  Every  teacher  may  with  profit  read  it  himself, 
and  selections  from  it  may  be  read  to  the  class. 

In  teaching  this  and  the  following  chapter,  the  teacher  should 
bear  in  mind  the  importance  of  fixing  quiet,  orderly  habits  of 
mental  work  in  order  that  there  may  be  no  waste  of  nervous  energy 
through  excitement  and  overeagerness.  Some  teachers  who  are 
very  successful  in  imparting  information  fatigue  their  pupils  unduly 
through  the  tense,  nervous  atmosphere  of  the  school.  This  is  com- 
ing to  be  recognized  as  an  important  point  in  school  hygiene. 


CHAPTER  ELEVEN 

THE  CARE  OF  THE  NERVOUS  SYSTEM 


FlG.  84.    There  is  no  truth  in  the  idea  that  a  person  can  have  too  much 
natural  sleep. 

SUPPOSE  that  you  decide  to  raise  your  hand.  The 
hand  comes  up.  Can  you  explain  exactly  what  made  it 
rise  ?  It  is  in  reality  a  very  complicated  action,  and  to 
make  sure  that  you  understand  it  we  will  go  through  the 
different  steps  in  it  with  you. 

First  of  all,  you  decided  to  raise  your  hand.  This  was 
an  act  of  the  mind.  Then  nerve  impulses,  whatever 
they  may  be,  were  started  out  from  the  brain.  These 
impulses  traveled  down  through  the  medulla  and  spinal 
cord,  passed  out  into  the  nerves  of  the  arm,  and  finally 
entered  the  muscle  cells.  This  caused  the  muscle  cells 
to  contract  and  lift  the  arm.  The  muscle  did  the  work, 
but  the  nervous  system  decided  what  was  to  be  done  and 
caused  the  muscle  to  do  it. 

In  all  our  other  activities  we  find  that  the  nervous 
system  plays  a  guiding  and  controlling  part.  The  regu- 
lation of  the  body  heat ;  the  secretion  of  the  digestive 


102 


THE  CARE  OF  THE  NERVOUS3 SYSTEM       103 

juices  ;  the  excretion  of  the  wastes ;  all  these  processes, 
as  well  as  every  movement  that  we  make,  are  under  the 
control  of  the  nervous  system.  We  must,  therefore,  keep 
the  nervous  system  in  health ;  for  when  it  goes  wrong 
in  its  work,  the  whole  body  suffers.  Fortunately  for  us, 
our  nervous  systems  are  splendidly  built,  and  on  the 
whole  they  do  their  work  faithfully  and  well.  There 
are,  however,  certain  points  in  the  care  of  them  in  which 
many  persons  fail,  and  we  ought  to  have  an  understand- 
ing of  these  points. 

Sleep  necessary  for  the  nervous  system.  The  cells  of 
the  nervous  system  must  have  sleep  to  build  themselves 
up  for  further  work,  and  so  far  as  we  know  they  are  the 
only  part  of  the  body  that  needs  sleep.  The  amount 
of  sleep  needed  varies  greatly  in  different  persons 
and  in  persons  of  different  ages.  A  little  baby  may 
sleep  as  much  as  twenty-two  out  of  the  twenty-four 
hours.  At  six  months  of  age  he  sleeps  about  sixteen 
hours.  At  seven  years  of  age  a  child  should  sleep  eleven 
or  twelve  hours ;  at  ten  or  twelve  years  of  age,  at  least 
ten  hours.  Older  persons  should  take  the  amount  of 
sleep  that  they  find  best  for  them.  Occasionally  a  per- 
son is  found  who  keeps  in  good  health  on  four,  five>  or 
six  hours  of  sleep.  Other  persons  must  have  eleven  or 
twelve  hours.  Each  one  should  go  to  bed  early  enough 
not  to  feel  sleepy  when  getting-up  time  comes ;  for  there 
is  no  truth  in  the  idea  that  one  can  have  too  much 
healthy  sleep.1 

Are  you   still  tired  and  sleepy  when  you  waken  in 

1  Illness  and  poisons  absorbed  from  the  intestines  cause  drowsiness. 
When  a  person  is  sleepy  from  one  of  these  causes,  the  condition  is,  of 
course,  an  unnatural  one. 


104 


OF  PHYSIOLOGY 


the  morning  ?  Are  you  pale  and  languid  and  do  you  drag 
yourself  through  your  work  ?  If  you  are,  it  may  be 
because  you  are  cutting  your  sleep  short ;  for  there  are 
thousands  of  people  who  are  starving  for  sleep  as  truly 
as  other  people  are  starving  for  food  and  fresh  air.  If 
you  have  fallen  into  a  habit  of  staying  up  late  in  the 


FIGS.  85  and  86.    A  change  for  a  time  to  a  different  kind  of  occupation  is  rest- 
ful to  the  nervous  system. 

evenings,  break  this  habit  and  go  to  bed  early.  A 
runner  or  a  baseball  team  that  has  been  losing  sleep 
has  not.  the  slightest  chance  of  winning  from  others  of 
equal  ability  who  have  had  a  sufficient  amount  of  it. 
This  is  because  the  nervous  system,  when  it  lacks  sleep, 
is  out  of  condition  and  cannot  control  the  muscles  as 
it  should. 

Rest  necessary  to  the  health  of  the  nervous  system. 
A  great  amount  of  nervous  energy  is  required  to  drive 
the  more  than  five  hundred  muscles  of  the  body,  and 
when  we  study  or  do  other  brain  work,  it  is  the  nervous 
system  that  is  called  into  action.  In  either  physical  or 


THE  CARE  OF  THE  NERVOUS  SYSTEM       105 

mental  work,  therefore,  we  tire  the  nervous  system,  and 
we  ought  not  to  continue  either  until  our  cells  are  poi- 
soned with  the  "fatigue  toxins  "  that  appear  in  the  body 
in  cases  of  exhaustion. 

Factory  workers  who  are  forced  to  speed  themselves 
up  to  machines,  and  little  children  in  schools  where  the 
recitation  periods  and  the  school  days  are  too  long, 
suffer  from  fatigue  and  cannot  do  their  best  work. 
Many  earnest,  ambitious  individuals  who  are  trying 
to  do  the  very  best  work  of  which  they  are  capable, 
injure  themselves  and  lower  their  working  power  by 
keeping  their  nervous  systems  exhausted.1  In  general, 
it  has  been  found  best  to  work  hard  during  regular 
working  hours,  and  then  to  have  rest  periods  when 
something  entirely  different  is  done.  In  schools  there 
should,  therefore,  be  rest  and  play  periods  for  young 
children,  and  older  persons  ought  to  work  certain  hours 
every  day  and  then  for  a  time  have  a  different  kind  of 
occupation. 

Fresh  air  helpful  in  resting  the  nervous  system.  A 
nerve  fiber  from  a  frog  will  carry  impulses  all  day 
without  fatigue  if  it  is  exposed  to  the  air  so  that  it 
can  take  in  the  oxygen  that  it  needs.  If  the  supply  of 
oxygen  be  cut  off  from  it,  however,  it  soon  becomes  ex- 
hausted. Undoubtedly  children  in  open-air  schools  can 
do  more  work  without  becoming  tired  than  can  children 
in  indoor  schools,  and  it  is  the  belief  of  those  who  sleep 

1  In  some  factories  it  has  been  found  that  the  workmen  can  accomplish 
more  when  they  work  eight  hours  than  when  they  work  ten  hours,  be- 
cause when  they  work  the  longer  hours  they  are  always  tired  and  never  in 
good  condition.  The  number  of  hours  that  is  best  for  a  working  day 
must,  of  course,  vary  with  the  kind  of  work  and  with  the  kind  of  people 
who  are  doing  the  work. 


io6 


PRIMER   OF  PHYSIOLOGY 


in  the  open  air  that  they  need  about  an  hour's  less  sleep 
than  they  require  if  they  sleep  indoors.  These  facts  in- 
dicate that  fresh  air  is  an  aid  in  preventing  exhaustion, 
and  that  tired  nerve  cells  are  more  quickly  rested  and 
built  up  when  the  body  is  given  plenty  of  outdoor  air. 

A  peaceful  mind  necessary  for  health.     In  our  study 
of  the  nervous  system  we  must  always  keep  in  mind 


FIG.  87.  Both  the  child's  pleasure  at  seeing  the  toy  and  the  man's  pleasure  at 
seeing  the  child's  happiness  affect  the  mind,  and  through  the  mind  affect  the 
body. 

that  it  has  the  double  function  of  governing  the  body 
and  of  acting  as  the  organ  of  the  mind.  It  is  perhaps 
economical  to  have  these  two  different  kinds  of  work 
done  by  the  same  system,  but  this  plan  has  its  drawbacks 
as  well  as  its  advantages;  for  the  condition  of  the 
mind  greatly  affects  and  sometimes  interferes  with  the 
proper  regulation  of  the  body. 

Good  news  or  bad  news  may  greatly  change  the  beat- 
ing of  the  heart.  A  toy  that  pleases  a  child  will  cause 
his  whole  body  to  tingle  with  pleasure,  and  will  cause 
impulses  to  pass  out  to  his  muscles  that  will  make  him 


THE  CARE  OF  THE  NERVOUS  SYSTEM       107 

laugh  and  clap  his  hands.  Food  that  is  pleasing  to  the 
taste,  or  even  the  sight  or  smell  of  food,  will  cause  the 
" -mouth  to  water,"  which  is  another  way  of  saying  that 
it  causes  the  digestive  juice  to  flow  from  the  salivary 
glands.  Experiments  on  a  dog  have  shown  that  the 
sight  and  smell  of  food,  even  though  the  food  does  not 
reach  the  stomach  at  all,  causes  an  abundant  flow  of  the 
digestive  juices  in  the  stomach;  while  in  a  dog  that  was 
made  angry  by  having  a  cat  placed  near  it  when  it  was 
eating,  the  flow  of  the  juice  in  the  stomach  was  inter- 
fered with  for  two  whole  days.  All  these  facts  show 
that  anger,  sorrow,  and  worry  interfere  with  the  proper 
action  of  the  body;  that  the  mind  greatly  affects  the 
body;  and  that  a  cheerful,  quiet,  hopeful  mind  is  neces- 
sary for  health. 

At  the  same  time,  we  must  realize  that  sickness  is  a 
real  thing,  and  that  when  it  comes  upon  us  we  cannot 
depend  upon  the  mind  alone  to  restore  us  to  health. 
When  a  child  has  diphtheria,  only  antitoxin  will  save  its 
heart  from  being  poisoned,  and  when  tuberculosis  attacks 
the  lungs,  good  food,  fresh  air,  ancl  rest,  as  well  as 
cheerfulness  and  hope,  are  needed  if  the  body  is  to 
make  a  winning  fight  against  the  germs.  When  the 
kidneys  have  been  poisoned  by  scarlet  fever  or  by  the 
use  of  alcoholic  drinks,  nothing  that  we  can  think  about 
them  will  make  them  able  to  throw  the  wastes  out  of 
the  body  as  a  pair  of  sound  kidneys  are  able  to  do. 
The  mind  cannot  take  poisons  out  of  the  body ;  it  can- 
not kill  germs  that  get  into  the  body.  These  things 
the  body  must  do  for  itself,  and  all  that  the  mind  and 
the  nervous  system  can  do  is  to  help  to  keep  each  or- 
gan of  the  body  at  work  at  its  particular  task. 


IO8  PRIMER   OF  PHYSIOLOGY 

Nevertheless,  it  is  true  that  the  nervous  system  rules 
the  whole  body;  that  when  the  nervous  system  goes 
wrong,  the  whole  body  goes  wrong;  and  that  just  as 
food,  fresh  air,  exercise,  and  rest  are  necessary  to  the 
health  of  the  body,  so  a  peaceful,  hopeful  mind  is 
necessary  in  order  that  the  nervous  system  may  remain 
in  health  and  regulate  all  the  body  parts  properly. 

QUESTIONS 

What  part  of  the  body  needs  sleep?  How  much  sleep 
should  a  baby  have  ?  a  child  seven  years  old  ?  a  child  twelve 
years  old  ?  an  adult  ? 

Why  is  rest  necessary  for  the  nervous  system  ?  Under  what 
conditions  of  work  and  rest  can  a  person  do  the  best  and 
most  work?  Give  three  facts  indicating  that  open-air  life  pre- 
vents exhaustion  of  the  nerve  cells. 

What  is  the  effect  of  joy,  hope,  and  other  pleasant  emotions 
on  the  nervous  system?  What  is  the  effect  of  anger,  sorrow, 
or  worry  ?  What  mental  state  is  necessary  to  the  health  of  the 
body?  Mention  some  experiments  with  animals  that  prove 
this.  Can  the  mind  take  poison  out  of  the  body  ?  Can  it  kill 
germs?  How  can  the  mind  help  the  body  to  do  these  things? 

SUGGESTIONS   TO   THE  TEACHER 

Emphasize  the  fact  that  nerve  cells  have  the  same  needs  as  the 
other  cells  and  that  any  trouble  in  other  parts  of  the  body  is  bound 
to  damage  the  nervous  system.  Dr.  Thomas  D.  Wood  of  Columbia 
University  estimates  that  "  15,000,000  out  of  the  20,000,000  children 
in  the  schools  of  the  United  States  need  attention  for  physical  de- 
fects which  are  partially  or  completely  remediable."  Insist  on  the 
evil  effects  of  pain  and  ill-health  on  the  nervous  system,  and  use 
this  as  an  argument  for  avoiding  infections  and  for  giving  attention 
to  adenoids,  decayed  teeth,  painful  feet,  defective  eyes,  and  other 
physical  defects. 


CHAPTER    TWELVE 

THE  EYE 

MANY  of  the  messages  which  travel  up  the  nerves  to 
the  brain  are  started  within  the  body  itself,  and  cause 
sensations  that  tell  us  about  the  condition  of  the  body. 
Examples  of  sensations  of  this  kind  are  sleepiness, 
fatigue,  weakness,  faintness,  hunger,  thirst,  and  nausea. 

Others  of  the  messages  that  come  to  the  brain  are 
started  in  the  nerves  by  things  that  are  outside  the  body, 
and  these  messages  bring  us  information  about  the  out- 
side world.  The  nerves  that  carry  these  messages  are 
the  nerves  of  sight,  hearing,  touch,  taste,  and  smell. 
Seeing,  hearing,  touching,  tasting,  and  smelling  are  the 
five  special  senses,  and  the  eye,  the  ear,  the  nose,  the 
mucous  membrane  of  the  mouth,  and  the  skin  are  the 
special  sense  organs. 

The  brain  dependent  on  the  sense  organs  for  informa- 
tion. Through  the  special  sense  organs  we  learn  all  that 
we  know  of  the  world  about  us,  and  when  anything  in- 
terferes with  the  proper  working  of  these  organs,  much 
information  that  ought  to  come  to  the  brain  fails  to 
reach  it.  Many  children  who  are  thought  to  be  stupid 
'are  dull,  not  because  they  have  slow  brains,  but  because 
their  eyes  and  their  ears  are  not  quick  in  gathering  the 
information  that  is  necessary  to  make  them  intelligent. 
We  must  learn  to  care  for  our  sense  organs,  especially 
for  our  eyes  and  ears,  for  without  them  the  brain  sits  in 
idleness,  and  is  no  more  certain  of  what  is  the  right  thing 
to  be  done  than  is  the  commander  of  an  army  whose 
scouts  bring  him  no  news  of  the  enemy's  movements. 

The  nerves  in  the  eye  stimulated  by  light.  Light  is 
waves  in  the  ether  which  fills  all  space,  and  the  eye 

109 


1 10  PRIMER   OF  PHYSIOLOGY 

is  an  instrument  so  constructed  that  when  light  enters 
it  the  nerves  of  sight  are  stimulated  and  messages  are 

started  to  the  brain.  These 
messages  give  us  a  series  of 
pictures  of  the  world  about  us, 
from  which  we  learn  about 
the  color  and  the  form  of  ob- 
gland  jects,  about  their  movements 
•nasal  cavity  and  their  nearness  to  us.  From 
these  pictures  much  of  our 
FIG.  88.  The  tear  gland  and  the  knowledge  comes.  Much  of 
duct  that  carries  the  tears  to  the  the  pleasure  also  that  we  have 

nose.  .. 

in  the  world  comes  from  them  ; 

for  just  as  music  starts  messages  from  the  ear  that  give 
pleasure  to  the  mind,  so  beautiful  objects  start  messages 
from  the  eye  that  are  pleasing  to  us.  Years  ago,  a  great 
man  of  science  suggested  that  we  should  have  concerts  of 
beautiful  colors  for  the  eyes  as  well  as  concerts  of  music 
for  the  ears.  Such  concerts  have  already  been  attempted. 
The  protection  of  the  eyes.  The  eyes  are  protected 
from  blows  by  the  deep  sockets  in  which  they  lie,  and 
by  cushions  of  fat  on  which  they  rest  and  turn.  They 
are  protected  from  dust  and  sweat,  and  screened  from 
light,  by  the  eyelids,  the  eyelashes,  and  the  eyebrows. 
In  the  outer  corner  of  each  of  the  upper  eyelids  is  a 
small, gland  which  secretes  the  tears.  These  flow  across 
the  eyes  to  the  inner  corners,  and  run  down  a  little  duct 
into  the  nose.  In  their  passage  across  the  eye,  the  tears 
wash  away  dust  and  germs.  In  the  eyelids  are  glands, 
very  similar  to  the  glands  that  oil  the  hair,  which  pour 
out  oil  along  the  edges  of  the  eyelids.  Sometimes  these 
glands  become  diseased,  and  the  secretion  from  them 


THE  EYE  III 

dries  and  forms  scales  around  the  roots  of  the  eyelashes. 
The  trouble  in  cases  of  this  kind  is  that  germs  are  grow- 
ing in  the  gland.  Dropping  a  solution  of  boracic  acid 
(as  much  as  will  dissolve  in  water)  into  the  eyes  will 
help  to  kill  the  germs. 

The  muscles  of  the  eye.  The  eye  is  moved  about  by 
six  muscles.  The  back  ends  of  these  muscles  are  at- 
tached to  the  eye  sockets. 
The  front  ends  are  at- 
tached to  the  ball  of  the 
eye.  These  muscles  can 
turn  the  eye  in,  out,  up, 
or  down.  It  is  not  nec- 
essary always  to  turn  the  optic  nerve 

head     toward     an     object     FlG-  89-     The  muscles  that  move  the  eye. 

which  we  wish  to  see  ;  for  the  eye  muscles  can  turn 
the  eye  toward  it  while  the  head  is  at  rest. 

In  some  persons  from  birth  the  sight  of  one  eye  is 
better  than  that  of  the  other  eye.  Such  a  person  may 
fall  into  the  habit  of  using  only  his  good  eye,  and  the 
muscles  of  the  weak  eye  will  not  turn  it  toward  the 
objects  he  looks  at.  A  person  whose  eyes  behave  in  this 
way  is  said  to  squint,  or  to  be  cross-eyed.  Usually  the 
trouble  can  be  remedied  if  it  is  taken  in  time,  but  if  it  is 
not  attended  to  in  very  early  life  the  sight  of  the  defec- 
tive eye  will  be  lost.  A  little  child  with  this  trouble 
should,  therefore,  have  proper  treatment  at  the  earliest 
possible  date. 

The  structure  of  the  eye.  The  eye  has  a  tough,  white 
outer  coat  called  the  sclerotic  coat ;  a  dark  middle  coat 
called  the  choroid  coat ;  and  lining  the  back  two  thirds 
of  the  eye,  a  delicate  inner  coat  called  the  retina.  The 


112 


PRIMER   OF  PHYSIOLOGY 


front  part  of  the  sclerotic  coat,  which  is  called  the 
cornea,  is  transparent  like  glass,  and  we  look  out,  or 
rather  the  light  comes  in,  through  a  little  window  that 
is  like  a  small  round  watch  crystal  on  the  front  of  the  eye. 


sclerotic  coat 


ins 


muscles 


FIG.  90.    A  diagram  showing  the  structure  of  thfe  eye. 

Inside  the  eye  is  found  a  circular,  clear  structure 
called  the  lens,  which  is  fastened  by  ligaments  to  the 
choroid  coat.  The  lens  and  the  ligaments  that  sup- 
port it  divide  the  eye  into  a  small  front  chamber  and  a 
large  back  chamber.  The  front  chamber  is  filled  with 
a  watery  liquid,  called  the  aqueous  humor.  The  back 
chamber  contains  a  clear  jelly-like  substance  called  the 
vitreous  humor.  The  nerves  of  sight  enter  at  the  back 
of  the  eye  and  spread  out  in  the  retina.  The  light 
reaches  these  nerves  and  starts  messages  in  them  by 
passing  in  through  the  cornea,  the  aqueous  humor,  the 


THE  EYE 


113 


lens,  and  the  vitreous  humor,  and  striking  against  the 
retina. 

The  iris  and  the  pupil.  The  front  part  of  the  choroid 
coat  is  called  the  iris.  This  shows  through  the  clear 
cornea,  and  the  person  is  black-eyed, 
brown-eyed,  or  blue-eyed  according 
to  the  color  of  his  iris.  In  the  center 
of  the  iris  is  a  circular  opening  called 
the  pupil.  Through  this  the  light 
passes  into  the  eye.  Muscles  in  the 
iris  regulate  the  size  of  the  pupil  ac- 
cording to  the  brightness  of  the  light, 
Examine  your  own  eyes  after  being 
in  a  bright  light  and  again  after 
being  in  a  weak  light,  and  you  will 
have  no  trouble  in  seeing  the  differ- 
ence in  the  size  of  the  pupils. 

The  image  formed  by  the  lens  on 

_  -  .     ' 

the  retina.  If  you  were  to  focus  a 
camera  on  a  group  of  objects,  as  for  example  a  house 
with  trees  surrounding  it,  and  then  look  at  the  ground 
glass  in  the  back  of  the  camera,  you  would  see  an  image 
of  the  scene  that  lies  before  the  camera.  The  image 
would  be  upside  down,  and  the  right  and  left  sides 
would  be  reversed,  but  the  house  and  the  trees  would 
be  there,  each  with  its  own  colors,  and  each  in  the  right 
position  in  the  group.  The  lens  in  the  front  of  the 
camera  forms  this  image  by  gathering  up  all  the  light 
that  comes  into  the  camera  from  each  of  the  objects, 
and  bringing  the  rays  together  so  as  to  form  a  picture  of 
all  the  objects. 

In  the  same  way,  the  lens  of  the  eye  forms  on  the 


FlG- 


1.   The  iris  and 

the  pupil. 


114 


PRIMER   OF  PHYSIOLOGY 


retina  images  of  the  objects  that  we  see.     In  the  eye, 
as  in  the  camera,  the  images  are  upside  down,  but  they 

are  there  in  their  proper  col- 
ors, and  the  different  objects 
have  the  right,  sizes  and  the 
right  positions  in  regard  to 
each  other.  This  picture  of 
whatever  we  are  looking  at 
starts  impulses  in  the  nerves 
of  sight  to  the  brain,  and 
when  these  messages  are  re- 
ceived by  the  brain,  we  form 
judgments  about  the  size, 
color,  and  form  of  the  ob- 
jects, and  say  that  we  see 
the  objects.  By  means  of 
the  images  in  the  eyes  we 
can  judge  also  of  the  dis- 
tances of  objects  from  us,  of 
their  movements,  and  of  their 
smoothness  or  roughness. 

The  shape  of  the  lens 
changed  in  looking  at  far  and 
near  objects.  In  looking  at 


FlG.  92.  The  lens  in  the  camera 
forms  inverted  images  on  the  ground 
glass  in  the  back  of  the  camera. 


a  near  object  the  lens  of  the  eye  must  be  rounded  up, 
and  in -looking  at  a  far  object  it  must  be  flattened.  This 
rounding  and  flattening  of  the  lens  is  done  by  little  mus- 
cles in  the  eye  which  loosen  and  tighten  the  ligament 
that  supports  the  lens.  If  you  should  fill  a  small  sack 
with  water  and  then  pull  on  the  ends  of  the  sack,  you 
would  flatten  it;  and  if  you  should  then  stop  pulling 
on  the  ends  of  the  sack,  the  sack  would  of  itself  round 


THE  EYE  115 

up.  So  in  the  eye,  when  the  ligament  is  loosened,  the 
lens  becomes  rounder.  This  change  in  the  shape  of 
the  lens  is  called  the  accommodation  of  the  eye,  be- 
cause by  it  the  eye  is  accommodated  to  the  nearness 
or  farness  of  the  object. 

Near-sightedness,  far-sightedness,  and  astigmatism.  In 
a  camera,  if  you  move  the  lens  too  far  forward  or  back- 
ward, the  image  becomes  blurred.  So  in  the  eye  the 
image  will  not  be  clear  and  the  vision  will  not  be  dis- 
tinct, unless  the  lens  is  the  right  distance  from  the  retina. 

The  eyes  of  some  persons  are  too  long  from  front  to 
back.  In  such  eyes  the  lens  is  too  far  from  the  retina 
and  the  image  is  indistinct.  These  persons  see  near 
objects  better  than  far  objects,  and  they  are  therefore 
said  to  be  near-sighted.  Any  one  who  bends  over  his 
book  in  reading,  or  who  holds  his  book  less  than  twelve 
inches  from  his  eyes,  is  near-sighted. 

The  far-sighted  eye,  on  the  other  hand,  is  too  short 
from  front  to  back,  and  the  lens  is  too  close  to  the 
retina.1  Persons  with  eyes  of  this  kind  see  distant  ob- 
jects best,  and  they  are  said,  therefore,  to  be  far-sighted. 

In  other  eyes,  the  curvature  of  the  cornea  is  not  the 
same  in  all  its  parts ;  that  is,  some  parts  of  it  are  flatter 
than  other  parts.  Rays  of  light  that  pass  through  this 
uneven  cornea  cannot  all  be  brought  to  a  focus  at  one 
point,  and  a  clear  image  is  impossible  in  such  an  eye. 
This  trouble  is  called  astigmatism.  It  is  a  very  com- 
mon defect  in  the  eye  and  may  be  found  alone,  or  along 
with  either  near-sightedness  or  far-sightedness. 

Necessity  for  a  clear  image  in  the  eye.     If  a  sharp, 

1  In  some  cases  of  near-sightedness  and  far-sightedness  the  trouble  may 
be  in  the  shape  or  the  refracting  power  of  the  lens. 


116 


PRIMER   OF  PHYSIOLOGY 


clear  image  is  not  formed  on  the  retina  of  the  eye,  seri- 
ous troubles  follow.  The  muscles  in  the  eye  keep  pull- 
ing and  working  to  try  to  change  the  shape  of  the  lens 
so  that  the  vision  will  be  clear ;  in  reading  it  is  a  strain 
on  the  attention  to  tell  what  letters  are  in  the  words, 
and,  in  general,  it  makes  all  work  that  requires  close 
attention  more  difficult.  This  overworks  and  deranges 
the  nervous  system,  and  soon  the  health  of  the  whole 


FIGS.  93  and  94.    There  are  5,000,000  school  children  in  the  United  States 
who  need  glasses. 

body  is  injured.  Two  of  the  most  common  symptoms 
of  eyestrain  are  headache  and  trouble  with  the  digestion, 
often  accompanied  by  dizziness  and  vomiting. 

The  importance  of  spectacles.  It  is  often  said  that 
the  great  amount  of  close  work  that  people  now  do 
injures  their  eyes,  and  it  is  insisted  that  the  eyes  of 
school  children  in  particular  are  damaged  by  the  work 
that  they  are  required  to  do.  There  is  doubtless  some 
truth  in  this  statement,  but  it  is  also  true  that  many  eyes 
are  naturally  defective.  Examination  of  the  eyes  of  the 
Indians  who  come  direct  from  the  plains  to  Hampton 
Normal  School,  in  Virginia,  shows  that  34.6  per  cent 


THE  EYE  II/ 

of  them  are  in  need  of  glasses  to  improve  their  vision 
or  to  relieve  eyestrain. 

It  is  estimated  that  there  are  5,000,000  school  children 
in  the  United  States  who  have  defective  eyes.  Nothing 
can  be  done  for  these  eyes  except  to  put  glasses  before 

CUFF 


p  n  T  r  3 


O    U    D    3 

FlG.  95.    You  should  be  able  to  read  the  upper  line  at  a  distance  of  30  feet, 
and  the  two  lower  lines  at  a  distance  of  20  feet. 

them  that  will  cause  clear  images  to  fall  upon  the 
retinas.  We  shall  not  attempt  to  explain  the  kinds  of 
glasses  that  are  used  to  correct  the  different  kinds  of 
eye  trouble,  but  it  is  an  easy  matter  for  a  good  oculist 
to  select  the  kind  of  lens  that  each  eye  needs.  Test 
your  vision  with  the  letters  given  on  this  page,  and  if 
you  have  reason  to  believe  that  you  need  glasses,  try  to 
get  them  ;  for  if  glasses  are  put  on  in  time,  many  cases 


Il8  PRIMER   OF  PHYSIOLOGY 

of  astigmatism  and  near-sightedness  will  be  outgrown, 
while  if  these  troubles  are  neglected,  the  shape  of  the 
eye  may  be  so  spoiled  that  the  person  will  be  compelled 
to  wear  glasses  all  his  life. 

The  eyes  injured  by  disease  germs.  In  measles, 
scarlet  fever,  and  smallpox,  the  germs  grow  in  the  eyes. 
During  the  progress  of  these  diseases  the  eyes  should 
be  rested  and  shielded  from  a  bright  light,  and  when 
the  eyes  have  been  severely  attacked,  they  should  not 
be  used  until  recovery  is  complete.  "  Pink  eye  "  is  a 
highly  infectious  disease  that  often  leaves  the  eyes  red 
and  inflamed  for  life.  It  is  spread  by  germs  that  are 
passed  from  one  person  to  another,  and  a  child  with 
"pink  eye"  ought  not  to  be  in  school.  Trachoma,  or 
"granulated  lids,"  is  another  germ  disease  of  the  eyes 
that  is  greatly  to  be  feared.  It  is  infectious,  and  it  is 
unsafe  to  be  around  a  person  who  is  suffering  from  it. 
Do  not  wash  your  eyes  in  a  public  wash  basin ;  do  not 
touch  a  public  towel ;  do  not  touch  your  eyes  with  dirty 
hands ;  and  do  not  touch  the  hands,  the  pencil,  or  the 
books  of  any  one  who  has  sore  eyes. 

Importance  of  a  good  light  while  working.  To  read 
or  to  work  by  a  dim  light  is  very  injurious  to  the  eyes. 
Too  bright  a  light  also  is  injurious,  especially  if  one 
faces  it,  and  a  flickering  light  of  any  kind  is  bad.  In 
writing  one  ought  to  sit  so  that  the  light  comes  over  the 
left  shoulder ;  for  then  the  shadow  of  the  hand  will  not 
interfere  with  the  work.  Facing  a  window  in  the  day- 
time, or  a  lamp  at  night,  is  hard  on  the  eyes.  Reading 
on  into  the  twilight  is  a  great  strain  on  the  eyesight, 
and  one  ought  not  to  seat  himself  carelessly  too  far 
from  the  light  when  doing  close  work  at  night. 


THE  EYE 


119 


One  difficulty  when  the  light  is  too  dim  is  that  the 
work  is  kept  so  close  to  the  eyes  that  there  is  a  great 
strain  on  the  muscles  that  turn  the  eyes  inward ;  for  the 
closer  an  object  is  to  the  eyes,  the  more  must  the  eyes 
be  turned  inward  to  focus  both  of  them  on  it  at  the 
same  time.  Keeping  the  work  close  to  the  eyes  is 


FIG.  96.     A  good  light  while  reading  is  important. 

especially  injurious  in  the  case  of  little  children;  for 
their  eyes  are  soft  and  easily  pulled  out  of  shape,  and 
the  muscles  tugging  at  the  eyes  to  turn  them  inward 
spoil  the  shape  of  the  globe  of  the  eye  and  cause  astig- 
matism. To  prevent  this,  school  books  for  young  chil- 
dren ought  to  be  printed  in  type  large  enough  so  that 
the  children  will  not  have  to  keep  the  books  close  to 
their  eyes  while  studying,  and  schoolrooms  should  be 
well  lighted.  The  rule  in  erecting  modern  school  build- 
ings is  to  allow  from  one  sixth  to  one  fourth  as  much 
space  for  windows  as  there  is  floor  space  in  the  room. 
Ribbed  glass  used  in  the  upper  sashes  assists  very 
greatly  in  spreading  the  light  evenly  over  the  room. 


120  PRIMER   OF  PHYSIOLOGY 

Resting  the  eyes  helpful  and  overtaxing  them  injuri- 
ous. When  we  have  been  reading  or  doing  other  close 
work  for  some  time,  it  benefits  the  eyes  greatly  to  stop 
for  a  few  moments  and  look  at  a  distant  object,  or  to 
gaze  into  the  distance  without  looking  at  anything  in 
particular.  Reading  on  a  moving  train  or  a  street  car 
quickly  tires  the  eyes,  because  the  distance  between 
the  book  and  the  eye  is  constantly  changing,  and  the 
muscles  in  the  eye  are  kept  busy  changing  the  shape 
of  the  lens.  Reading  while  lying  down  is  also  hard 
on  the  eyes,  because  the  book  or  paper  is  often  held  in 
such  a  position  that  the  eyes  must  be  strained  to  see 
it.  If  you  read  while  traveling  or  while  lying  down, 
rest  your  eyes  occasionally  and  stop  the  reading  be- 
fore the  eyes  have  become  fatigued. 

QUESTIONS 

How  are  the  eyes  protected  from  blows?  from  light  and 
dirt?  Where  are  the  glands  which  secrete  the  tears?  Of 
what  use  are  the  tears?  What  is  the  cause  of  scales  on  the 
edges  of  the  eyelids?  Explain  how  the  eye  is  moved.  What 
causes  a  person  to  squint?  Name  the  coats  of  the  eye.  De- 
scribe the  cornea ;  the  lens  ;  the  aqueous  humor  ;  the  vitreous 
humor ;  the  iris  ;  the  pupil.  In  what  part  of  the  eye  are  the 
nerves-  of  sight? 

Explain  how  images  are  formed  in  a  camera  and  in  the  eye. 
In  what  do  the  images  in  the  eye  start  messages?  What 
judgments  does  the  brain  form  from  these  messages  ? 

How  is  the  eye  accommodated  to  near  and  far  objects? 
What  causes  near-sightedness?  far-sightedness?  astigmatism? 
What  is  the  effect  on  one's  health  of  a  blurred  image  on  the 
retina?  How  many  school  children  in  the  United  States  need 


THE  EYE  121 

glasses?  Why  is  it  important,  aside  from  improving  the  health, 
that  glasses  be  worn  by  children  who  need  them  ? 

In  what  germ  diseases  are  the  eyes  infected  ?  How  should 
the  eyes  be  cared  for  in  these  diseases?  What  is  "  pink-eye  "  ? 
"  granulated  lids  "  ?  Name  some  things  that  should  be  avoided 
because  they  may  allow  germs  to  enter  the  eyes. 

From  what  direction  should  the  light  come  when  one  is 
working?  Why  is  it  harmful  to  read  or  work  by  a  dim  light? 
Why  is  work  that  is  held  close  to  the  eyes  especially  harmful 
to  little  children?  How  much  window  space  should  a  school- 
room have  ?  Why  is  it  harmful  to  read  on  a  moving  train  ? 
while  lying  down? 

SUGGESTIONS  TO  THE  TEACHER 

When  medical  inspection  is  lacking,  the  school  should  have  a 
vision  chart  for  examining  the  eyes.  This  is  usually  furnished  free 
by  city  and  state  superintendents,  or  a  copy  may  be  purchased  for 
ten  cents  from  World  Book  Company,  Yonkers,  New  York.  The 
following  directions  will  allow  a  rough  test  to  be  made  with  the  let- 
ters on  page  117:  — 

Have  a  good  light  on  the  letters  that  are  to  be  read.  Seat  the 
pupil  at  a  distance  of  20  feet  from  them.  Test  persons  wearing 
glasses  with  their  glasses  on.  Cover  one  eye  with  a  card  (but  do 
not  press  on  it)  while  the  other  is  being  tested. 

The  upper  line  should  be  read  at  a  distance  of  30  feet  and  the 
lower  lines  at  a  distance  of  20  feet.  In  case  either  eye  fails  to-  meas- 
ure up  to  this  standard,  glasses  are  needed.  Persons  who  cannot 
read  may  be  tested  by  asking  them  whether  the  letter  E  in  the  chart 
is  open  at  the  right,  left,  top,  or  bottom.  In  case  the  pupil  knows 
the  chart  by  heart,  cut  a  small  opening  in  a  piece  of  cardboard  and 
expose  only  one  character  at  a  time  while  the  test  is  being  made. 

Failure  to  read  the  letters  by  children  under  seven  years  of  age 
does  not  necessarily  mean  that  glasses  are  required. 

There  may  be  defects  of  the  eye  that  will  not  be  revealed  by  this 
test.  When  there  are  symptoms  of  eyestrain,  an  oculist  should  be 
consulted. 


CHAPTER   THIRTEEN 


THE  EAR 


FlG.  97.  The  light  waves  start  impulses  in  the  nerve  of  sight,  and  we  see 
the  lightning;  the  sound  waves  start  impulses  in  the  nerve  of  hearing,  and  we 
hear  the  thunder. 

DOUBTLESS  you  have  seen  a  flash  of  lightning  fall 
from  the  sky,  and!  have  stood  and  waited  until  the  roll- 
ing of  the  thunder  came  to  your  ears.  What  was  it 
that  came  to  your  eyes  and  caused  you  to  see  the 
lightning?  It  was  waves  in  the  ether.1  What  was  it 
that  came  to  your  ears  and  caused  you  to  hear  the 
thunder  ?  It  was  waves  in  the  air.  Why  can  you  not 
see  the  thunder  ?  It  is  because  the  eye  is  not  af- 
fected by  waves  in  the  air;  only  ether  waves  can  stimu- 
late the  nerves  of  sight.  Why  is  it  that  you  do  not 
hear  the  lightning  ?  It  is  because  ether  waves  do  not 
affect  the  ear ;  only  air  waves  stimulate  the  nerves  of 
hearing. 

1  Ether  is  an  invisible,  elastic  fluid  that  fills  all  space.  Light,  the  elec- 
tric waves  that  are  used  in  wireless  telegraphy,  and  the  X-ray  are  waves  in 
the  ether.  They  run  with  almost  incredible  speed,  light  traveling  at  the 
rate  of  186,000  miles  a  second.  Air  waves  are  very  much  slower  than 
ether  waves,  sound  waves  traveling  only  about  1120  feet  a  second. 

122 


THE  EAR 


123 


mastoid 
cavity 


inner  ear 


Through  the  ear  the  confusion  of  air  waves  that 
comes  from  the  instruments  of  an  orchestra  is  trans- 
formed into  music ;  through  it  we  are  able  to  under- 
stand the  thoughts  of 
a  friend  when  he,  by 
speaking,  sends  a 
series  of  air  waves  to 
us  across  a  room. 
In  the  whole  body 
chere  is  nothing  more 
wonderful  than  this 
instrument  that  has 
been  given  us  to  catch 
the  waves  in  the  air 
and  carry  their  motion 
to  the  nerves  of  hear- 
ing, which  lie  deep  in 
the  bones  of  the  skull. 
There  are  three  main  divisions  of  this  organ,  —  the  outer, 
the  middle,  and  the  inner  ear. 

The  outer  ear.  The  outer  ear  is  composed  of  carti- 
lage covered  with  skin.  It  catches  the  sound  waves 
and  turns  them  down  a  winding  canal  to  the  middle 
ear.  When  a  dog,  a  horse,  or  a  rabbit  is  listening, 
it  holds  up  its  ears  to  catch  the  sound  waves,  and 
a  man  sometimes  puts  his  hand  behind  his  ear  to 
help  in  catching  the  sound  and  turning  it  into  the 
ear. 

The  middle  ear.  The  middle  ear  is  a  little  drum- 
shaped  cavity  in  the  bone  of  the  skull.  It  is  filled  with 
air,  and  is  connected  with  the  throat  by  the  Eustachian 
tube.  At  the  inner  end  of  the  canal  that  leads  inward 


middle  ear    Eusta-  \ 
chian  tube 

FIG.  98.      Diagram  of  the  ear. 


124  PRIMER   OF  PHYSIOLOGY 

from  the  outer  ear  is  a  little  membrane  called  the  tym- 
panic membrane.  This  stretches  like  a  thin  skin  across 
the  bottom  of  the  canal  and  separates  the  outer  ear 
from  the  middle  ear. 

The  bone  of  the  skull  behind  the  middle  ear  is 
spongy  and  has  a  cavity  in  it  which  is  called  the 
mastoid  cavity.  This  opens  out,  like  a  little  chamber, 
from  the  middle  ear,  and  when  germs  infect  the  middle 
ear  they  often  reach  the  mastoid  cavity  also.  This 
trouble  is  called  mastoiditis.  In  cases  of  this  disease 
there  is  always  danger  that  the  germs  will  find  their 
way  to  the  brain  and  cause  meningitis. 

The  bones  of  the  ear.     Across  the  middle  ear  a  chain 
of   three   small    bones    stretches    from    the    tympanic 
membrane  to  the  inner  ear.     These 
bones  are  called  from  their  shape  the 
malleus  (hammer),  the  incus  (anvil), 
and  the  stapes  (stirrup).     The  malleus 
tympanic  -HjP     is   fastened    to   the    tympanic   mem- 
membrane  W       brane  ;  the  stapes  fits  into  an  opening 
..,  that  leads  into  the  inner  ear  ;  and  the 

FlG.  99.      The  chain 

of  bones  of  the  ear    incus  is  between  the  malleus  and  the 


connecting    with    the      gta  (Fi         gg^       After      we 

tympanic    membrane.  ,.     ,     ,  ,  f    , 

studied  the  plan  of  the  whole  ear,  we 
shall  learn  how  these  bones  carry  the  motion  of  the  sound 
waves  from  the  tympanic  membrane  to  the  inner  ear. 

The  inner  ear.  The  inner  ear  lies  deep  in  the  bone 
of  the  skull.  It  is  exceedingly  complicated  in  structure 
and  we  shall  not  attempt  to  explain  it  further  than  to 
say  that  it  has  three  parts,  —  a  central  part  called  the 
vestibule,  a  coiled  part  called  the  cochlea,  and  three 
semicircular  canals  at  the  back  that  wind  through  the 


THE  EAR 


125 


opening  for  stapes 
vestibule 
cochlea 


bone  of  the  skull.  The  entire  inner  ear  is  filled  with 
a  fluid,  and  the  fibers  of  the  nerve  of  hearing  end  in 
such  a  way  that  when  waves 

.  . 

are  set  up  in  the  fluid,  the  cular 
nerve  endings  are  stimulated 
and  messages  are  started  in 
them  to  the  brain. 

How  a  sound  wave  starts 
a  message  to  the  brain. 
When  a  sound  wave  strikes 
the  outer  ear,  it  is  turned 
down  the  canal  leading  to 
the  inner  ear;  it  then  strikes 

against   the  tympanic    mem-    FIG.     too.     The    inner    ear.       The 

brane  and  starts  it  to  swing-  Iower  fi&ure  shows  the  natural  size  of 

,    .  „,.  .  the  inner  ear. 

ing  out  and  in.      This  puts 

the  malleus,  the  incus,  and  the  stapes  in  motion,  and 
the  stapes  is  pushed  in  against  the  liquid  in  the  inner 
ear.  This  sets  up  waves  in  the  liquid,  and  the  beat- 
ing of  these  waves  stimulates  the  nerves  of  hearing  and 
starts  messages  to  the  brain.  When  these  messages 
reach  the  brain,  we  hear  the  sound. 

If  the  waves  in  the  air  are  large  and  strike  violently 
against  the  tympanic  membrane,  so  that  large  waves 
are  set  up  in  the  fluid  in  the  ear,  we  say  that  the  sound 
is  loud.  If  the  waves  are  small,  so  that  the  tympanic 
membrane  and  the  chain  of  bones  swing  gently  to  and 
fro,  the  nerves  are  stimulated  only  a  little,  and  the  sound 
is  soft.  Within  the  inner  ear  is  a  wonderful  mechanism 
which  is  so  arranged  that  a  sound  having  one  pitch  will 
start  messages  in  one  set  of  nerves,  and  a  sound  having 
a  different  pitch  will  start  messages  in  another  set  of 


126  PRIMER   OF  PHYSIOLOGY 

nerves.  By  this  arrangement  the  brain  is  able  to  tell 
the  pitch  of  the  different  sounds  that  come  to  it. 

Earache  and  running  ear.  Practically  all  ear  troubles 
are  in  the  middle  ear  and  are  caused  by  germs.  These 
germs  work  their  way  from  the  throat  into  the  ear 
through  the  Eustachian  tube,  and  they  grow  in  the 
lining  of  the  middle  ear  and  about  the  little  bones,  much 
as  they  grow  in  the  nose  when  we  have  catarrh. 
Frequently,  in  diseases  like  colds,  grip,  scarlet  fever, 
measles,  and  diphtheria,  the  ears  become  infected,  and 
in  these  cases  it  is  most  important  that  a  physician  give 
them  early  and  proper  care.  Often  it  is  adenoids  that 
start  ear  trouble,  and  in  chronic  cases  of  earache  or 
running  ears,  adenoids  should  be  looked  for. 

It  is  not  right  to  allow  children  to  suffer  needless  pain 
from  ear  troubles,  and  they  ought  not  to  be  left  to  out- 
grow them  ;  for  a  running  ear  already  has  a  hole  through 
the  tympanic  membrane,  and  the  hearing  is  in  danger 
of  being  lost.  Nearly  all  deafness  in  older  persons  is 
due  to  the  fact  that  when  these  persons  were  children, 
germs  were  allowed  to  grow  in  the  ears  until  they  dam- 
aged the  tympanic  membrane  or  the  bones  that  carry 
the  motion  of  the  sound  waves  to  the  inner  ear.  Some- 
times the  membrane  or  the  chain  of  bones  is  broken 
down,  or  destroyed.  Sometimes  the  trouble  is  that  the 
membrane  is  thickened  and  stiffened,  or  the  chain  of 
bones  is  stiffened  at  the  joints  until  the  movement  in  it 
is  wholly  or  partly  lost.  Among  grown  persons  about 
one  third  have  the  hearing  affected  in  one  or  both  ears. 
This  could  be  prevented  by  attending  to  the  ears  at  the 
proper  time. 

Other  points  in  the  care  of  the  ear.     Quinine,  if  taken 


THE  EAR 


127 


for  a  considerable  time,  may  cause  deafness,  and  this 
medicine,  like  other  medicines,  should  be  used  only 
when  prescribed  by  a  physician.  A  blow  on  the  side  of 
the  head  is  dangerous  to  the  hearing  ;  for  it  may  send 
so  strong  an  air  wave  down  the  canal  of  the  ear  that  the 


FlG.  101.      Testing  the  hearing. 

tympanic  membrane  may  be  broken.  Live  insects  in 
the  ear  cause  great  distress  by  buzzing  and  moving 
about.  They  should  be  drowned  by  pouring  warm 
water  into  the  ear. 

No  one  but  a  physician  should  attempt  to  remove 
objects  from  the  ear,  because  an  unskilled  person  in 
attempting  to  do  so  may  injure  the  lining  of  the  canal, 
or  break  the  tympanic  membrane.  In  the  canal  of  the 
ear  there  is  a  bitter  wax  secreted  to  protect  the  ear  from 
insects.  Children  sometimes  form  a  habit  of  picking 
at  their  ears  with  the  head  of  a  pin  or  other  object. 
This  causes  the  lining  to  become  inflamed  and  the  wax 
to  be  secreted  too  abundantly.  One  physician  has  said, 
"You  should  never  thrust  anything  smaller  than  your 
elbow  into  your  ear,"  and  another  has  added,  "  Before 
you  thrust  your  elbow  into  your  ear  you  should  wrap 
your  coat  around  it."  If  wax  accumulates  until  it  be- 
comes troublesome,  a  physician  should  be  consulted. 


128  PRIMER   OF  PHYSIOLOGY 

QUESTIONS 

Describe  the  outer  ear.  What  is  its  use?  Describe  the 
middle  ear.  What  separates  the  middle  ear  from  the  outer 
ear?  What  is  the  mastoid  cavity?  What  causes  mastoiditis? 
Name  and  describe  the  three  bones  of  the  middle  ear.  Where 
is  the  inner  ear?  Name  its  parts.  With  what  is  the  inner 
ear  filled? 

Where  do  the  nerves  of  hearing  end?  Explain  how  a  sound 
wave  stimulates  the  nerves  of  hearing.  What  is  the  difference 
between  a  loud  sound  and  a  soft  sound?  Explain  how  it  is 
possible  for  the  brain  to  understand  the  pitch  of  a  sound. 

How  do  germs  enter  the  ear?  In  what  parts  of  the  ear  do 
they  grow  ?  What  is  the  most  common  cause  of  earache  and 
running  ears?  What  is  the  cause  of  nearly  all  cases  of  deaf- 
ness in  grown  persons?  What  per  cent  of  adults  have  im- 
paired hearing? 

What  bad  effects  have  excessive  doses  of  quinine?  Why 
is  a  blow  on  the  side  of  the  head  dangerous  ?  What  damage 
may  be  done  when  an  unskilled  person  attempts  to  remove 
objects  from  the  ear?  What  is  the  use  of  the  bitter  wax  in  the 
ear  ?  What  damage  may  be  done  by  picking  at  the  wax  in  the 
ears? 

SUGGESTIONS  TO  THE  TEACHER 

In  schools  that  do  not  have  medical  inspection  the  teacher  should 
test  the  hearing.  This  may  be  done  either  with  a  watch  (Fig.  101) 
or  by  requiring  the  pupil  to  repeat  words  that  have  been  whispered 
to  him.  Each  ear  should  be  tested  separately.  It  should  be  im- 
pressed upon  the  pupils  that  deafness  is  rarely  curable  and  that  any 
ear  trouble  demands  medical  attention  at  once. 


CHAPTER   FOURTEEN 


THE  ORGANS  OF  TOUCH,   TASTE,   AND  SMELL 

THE  sight  and  the  hearing  are  especially  important 
because  they  give  us  knowledge  not  only  of  near  ob- 
jects, but  also  of  objects  that  are  far  away.  The  sense 
of  smell  may  also  give  us 
information  of  an  object 
when  it  is  at  a  distance; 
but  in  the  main  this  sense, 
as  well  as  the  sense  of 
taste  and  the  sense  of 
touch,  is  valuable  because 
it  enables  us  to  judge  of 
objects  that  are  near  at 
hand. 

There  is  not  much  that 
we  can  learn  about  any 
of  these  senses  that  is 
important  from  the  stand- 
point of  health.  It  is  in- 
teresting, however,  to 
know  something  of  the  way  in  which  the  messages  that 
cause  the  sensations  of  touch,  taste,  and  smell  are  started 
in  the  nerves,  and  to  understand  something  of  what  we 
learn  through  these  senses.  In  this  chapter  we  shall 
therefore  study  the  organs  of  touch,  taste,  and  smell. 

Touch.  The  sense  of  touch  is  the  most  widely  dis- 
tributed of  all  the  senses,  for  we  can  feel  through  the 
skin  on  every  part  of  the  body.  Through  the  sense  of 
touch,  even  better  than  through  the  eye,  we  can  learn 
the  form  of  objects ;  through  it  we  can  tell  whether  ob- 
jects are  smooth  or  rough,  whether  they  are  hot  or  cold. 

129 


FlG.  102.    A  blind  girl  reading  by  sense 
of  touch. 


130 


PRIMER   OF  PHYSIOLOGY 


Blind  persons  learn  to  read  by  passing  the  finger  tips 
over  raised  letters,  and  persons  who  are  both  blind  and 
deaf  gain  through  the  touch  much  of  the  information 
that  comes  to  others  of  us  through  the  eye  and  ear. 
The  touch,  therefore,  is  a  sense  that  is  not  only  at  all 
times  highly  useful  to  us,  but  one  that  can  be  fur- 
ther educated  and  in  time  of 
need  called  into  use  to  take 
the  place  of  other  senses. 

The  endings  of  the  nerves 
of  touch  in  the  skin.  The 
dermis,  or  lower  layer  of  the 
skin,  is  thrown  up  into  little 
peaks  called  papilla  (singular, 

FIG.  zo3.    A  ne'rve    fiber   ending  PaPilla~)  tha'   Stand   «P   Under 

around  the  bases  of  the  cells  in  the   the  epidermis.     Some  papillae 
epidermis.  contain   a    great   network   of 

little  blood  vessels.  Others  contain  a  touch  corpuscle, 
which  is  a  little  group  of  cells  with  a  nerve  fiber  wind- 
ing about  through  it  and  ending  in  it  (Fig.  76).  Other 
fibers  of  the  nerve  of  touch  divide  at  the  outer  end  into 
many  little  branches  which  end  freely  among  the  lower 
cells  of  the  epidermis,  or  spread  out  into  little  saucer- 
like  structures  around  the  bases  of 
some- of  these  cells  (Fig.  103). 

The  nerves  of  touch  are  especially 
abundant  in  the  fingers,  lips,  tongue, 
and  tip  of  the  nose,  and  in  these  places 
the  sense  of  feeling  is  most  acute. 
You  can  perform  some  interesting  ex- 
periments by  thrusting  two  or  three 
pins  through  a  piece  of  cork  or  wood 


FIG.  104. 


TOUCH,   TASTE,  AND  SMELL  131 

(Fig.  104)  and  trying  how  far  apart  you  must  place  them 
on  different  parts  of  the  body  to  enable  you  to  feel  the 
points  of  the  pins  separately. 

Messages  started  by  pressure  in  the  nerves  of  touch. 
When  we  touch  anything,  the  epidermis  is  pressed  down 
on  the  ends  of  the  nerves  of  touch.  This  starts  impulses 
to  the  brain,  and  when  these  impulses  arrive  in  the  brain 
they  cause  us  to  feel.  If  all  the  nerve  endings  that  are 
being  stimulated  have  the  same  amount  of  pressure  on 
them,  we  know  that  we  are  feeling  a  smooth  surface. 
If  some  of  them  are  being  pressed  harder  than  others, 
we  know  that  the  surface  is  rough.  When  we  are 
touching  an  object,  we  know  where  the  object  is,  be- 
cause we  know  from  what  part  of  the  body  the  messages 
are  coming.  We  know  whether  the  object  is  large  or 
small  by  the  extent  of  skin  surface  that  is  touching  it, 
and  by  the  distance  that  we  must  move  our  hands  to  pass 
them  over  it.  If  you  lay  your  hand  against  the  wall, 
messages  come  in  from  the  whole  front  of  the  hand,  and 
you  judge  that  you  are  touching  one  large  object.  If 
you  feel  two  objects,  like  the  points  of  two  pencils,  you 
know  that  there  are  two  of  them  because  the  messages 
come  from  two  places  in  the  skin  with  a  space  between 
them  in  which  the  nerves  are  not  being  stimulated. 

Mistaken  judgments  concerning  objects  that  we  touch. 
The  mind  can  make  mistakes  in  judging  of  the  messages 
that  come  in  through  the  nerves  of  touch  as  well  as  in 
forming  judgments  from  the  messages  that  come  in 
through  the  eye.  Cross  your  fingers  and  rub  them 
across  the  tip  of  your  nose  so  that  the  nose  is  between, 
the  two  fingers.  Can  you  explain  why  you  seem  to  feel 
two  noses  ? 


132  PRIMER   OF  PHYSIOLOGY 

Taste.  The  nerves  of  taste  are  in  the  mucous  mem- 
brane of  the  tongue  and  of  the  back  part  of  the  mouth. 
Before  anything  can  be  tasted,  it  must  first  be  dissolved. 
Then  it  works  its  way  down  among  the  cells  and  starts 
impulses  in  the  nerves  of  taste.  When  these  impulses 
reach  the  brain,  we  learn  whether  the  object  has  a  sweet, 
sour,  bitter,  or  salt  taste.  Many  of  the  supposed  tastes 
of  foods  are  in  reality  odors,  and  when  because  of  a  cold 
or  for  other  reasons  the  sense  of  smell  is  dull,  many  foods 
are  practically  tasteless.  The  continual  use  of  tobacco, 
alcoholic  drinks,  and  strong  condiments  like  pepper  and 
tabasco  sauce,  permanently  diminishes  the  sense  of 
taste. 

The  sense  of  smell.  The  sense  of  smell  is  probably 
the  keenest  of  all  our  senses.  It  is  likely  that  it  is  of 

use  chiefly  to  judge  whether 
or  not  our  food  is  in  proper 
condition  to  be  eaten,  and  to 
tell  whether  air  is  fit  to  be 
breathed.  Lower  animals, 
like  the  dog,  have  this  sense 
so  highly  developed  that  they 
can  follow  the  track  of  a  man 
or  other  animal  many  hours 
FIG.  105.  The  nerve  of  smell  end-  after  the  trail  has  been 

ing  in  the  mucous  membrane  of     made>       Among  men    individ- 
the  nasal  chamber. 

uals    differ    greatly     in    the 
sharpness  of  their  sense  of  smell. 

The  nerve  of  smell  stimulated  by  particles  in  the  air. 
What  we  call  an  odor,  or  a  smell,  is  in  reality  little  particles 
of  matter  floating  in  the  air.  These  particles  come  from 
a  rose,  from  our  food,  or  from  anything  that  we  smell, 


TOUCH,    TASTE,   AND  SMELL  133 

and  are  drawn  up  into  the  nasal  chambers  with  the  air. 
In  the  mucous  membrane  that  lines  the  upper  part  of 
these  chambers  are  found  the  olfactory  cells,  from  which 
nerve  fibers  run  to  the  brain.  When  odors  come  in  con- 
tact wij:h  the  olfactory  cells,  impulses  are  started  that 
cause  the  sensation  of  smell. 

Care  of  the  organ  of  smell.  When  the  delicate  olfactory 
cells  are  destroyed,  they  are  not  renewed,  and  the  sense 
of  smell  is  permanently  lost.  They  may  be  destroyed 
by  inflammation,  which  is  often  brought  on  by  inhaling 
dust  or  by  working  among  the  fumes  of  acids  or  other 
chemicals.  Exhaling  cigarette  smoke  through  the  nose 
is  also  very  injurious  to  the  cells,  and  many  ciga- 
rette smokers  have  little  or  no  sense  of  smell.  Another 
common  cause  of  the  loss  of  the  sense  of  smell  is  catarrh, 
which  ought  always  to  be  treated  by  a  good  physician 
and  not  allowed  to  run  on  from  year  to  year.  When 
the  throat  is  blocked  by  adenoids,  the  odors  of  foods 
cannot  enter  the  nose  as  they  should,  and  the  pleasure 
of  eating  is  to  a  considerable  extent  lost.  The  sense  of 
smell  is  valuable  to  us  both  because  of  the  pleasure 
that  we  receive  from  agreeable  odors  and  because  of 
the  warnings  that  come  to  us  in  the  way  of  disagree- 
able odors,  and  we  ought  to  try  to  keep  it  in  as  good 
working  condition  as  possible. 

QUESTIONS 

What  do  we  learn  through  the  touch?  What  is  a  papilla? 
Explain  how  the  nerves  of  touch  end  in  the  skin.  Where  are 
the  nerves  of  touch  most  abundant? 

When  we  touch  an  object,  how  are  the  impulses  started  in 
the  nerves?  How  do  we  judge  whether  an  object  is  .rough  or 


134  PRIMER   OF  PHYSIOLOGY 

smooth  ?  How  do  we  know  where  it  is  ?  How  do  we  judge 
of  its  size  ? 

Where  are  the  nerves  of  taste  ?  How  does  the  food  reach 
the  nerves  of  taste  ?  Why  can  we  not  taste  certain  foods  when 
we  have  a  cold?  How  may  the  sense  of  taste  be  injured? 

What  purpose  does  the  sense  of  smell  serve?  What  is  an 
odor?  Where  are  the  nerves  of  smell?  How  are  messages 
started  in  them?  How  may  the  sense  of  smell  be  injured? 

SUGGESTIONS  TO  THE  TEACHER 

If  the  class  has  time  for  them,  it  will  add  interest  to  the  work  to 
perform  a  few  simple  experiments  in  touch,  taste,  and  smell.  Direc- 
tions may  be  found  in  any  text  of  experimental  psychology.  Optical 
illusions  also  are  interesting  and  they  bring  to  the  attention  of  the 
pupil  the  part  played  by  the  brain  in  sensation. 

In  Figure  91  the  iris  may  appear  to  be  seen  from  either  front 
or  back,  and  other  optical  illusions  may  be  found  in  texts  of  psychol- 
ogy or  more  advanced  physiology.  Common  illusions  that  may  be 
called  to  the  pupil's  attention  are :  the  fact  that  the  letter  s  and  the 
figure  8  must  be  made  larger  at  the  bottom  to  prevent  their  seeming 
heavier  at  the  top;  that  the  sun  and  moon  appear  larger  on  the 
horizon  than  when  high  in  the  sky ;  that  from  a  railway  train 
the  landscape  seems  to  be  moving ;  and  that  when  one  looks  at  the 
moon  through  the  treetops  while  running,  the  moon  seems  to  run 
with  him. 


CHAPTER  FIFTEEN 

FOODS  AND  WHY  WE  NEED  THEM 


FlGS.  106  and  107.    The  windmill  gets  its  power  to  work  from  the  wind  which 
blows  against  it ;  the  man  gets  his  strength  from  the  food  that  he  eats. 


FROM  my  window  I  can  see  a  windmill  standing  with 
its  arms  outlined  against  the  sky.  A  little  while  ago 
it  was  whirling  rapidly  about  and  pumping  water  into 
the  tank  that  it  keeps  supplied.  Now  it  is  standing 
motionless  in  the  sunshine,  as  if  overcome  by  the  morn- 
ing heat.  Is  the  windmill  broken  ?  Or  has  anything 
happened  to  it  that  will  keep  it  from  any  longer  pump- 
ingVater  for  its  owner  ?  Not  at  all.  The  only  trouble 
is  that  the  wind  which  supplied  the  power  to  run  the 
mill  has  for  the  time  failed. 

Wherever  there  is  motion  and  whenever  work  is  done, 
power  to  cause  the  motion  and  to  do  the  work  must 
come  from  somewhere.  We  think  of  a  swift  and  heavy 
automobile  as  a  powerful  machine,  but  in  reality  the 
power  comes  from  the  gasoline  that  is  exploded  in 
the  cylinders,  and  when  the  supply  of  gasoline  gives 
out,  an  automobile  can  no  more  move  itself  than  can  a 
stone.  Every  other  machine,  whether  it  be  run  by 

US 


136 


PRIMER   OF  PHYSIOLOGY 


steam,  gasoline,  electricity,  water,  wind,  or  in  any  other 
way,  must  draw  the  power  that  runs  it  from  some 
source  outside  itself.  The  windmill  cannot  run  itself ; 
it  must  stand  and  wait  until  the  wind  comes  to  give 
it  motion  and  make  it  able  to  do  its  work. 

Food  as  a  source  of  power.  The  human  body  has 
strength.  It  moves  and  does  work.  It  cannot  furnish 
itself  with  power,  however,  so  we  must  have  some  source 


FIGS.  108  and  109.    Food  is  necessary  to  furnish  material  for  the  repair  and 
growth  of  the  cells,  and  to  keep  up  the  body  heat. 

from  which  to  draw  the  strength  that  is  in  our  muscles. 
This  source  of  power  is  the  food  that  we  eat.  Food  is 
necessary  to  give  strength  to  the  body.  Without  it  the 
muscle  cells  cannot  contract  and  cause  the  movements 
of  the  body  parts. 

Food  as  fuel.  A  locomotive  as  it  thunders  past  us 
glows  with  warmth.  It  gets  its  warmth  from  the  fuel 
that  is  burned  under  its  boiler.  A  stove  with  a  fire  in  it 
gives  off  heat  to  all  the  room.  This  heat  comes  not 
from  the  stove  itself,  but  from  the  fuel  that  is  burned  in 
the  stove.  Your  own  body  is  warm,  as  you  know  from 


FOODS  AND    WHY  WE  NEED   THEM         137 

feeling  it.  The  heat  of  the  body  comes  from  the  food 
that  is  burned  within  the  cells.  Food  is  necessary  to  keep 
up  the  body  heat.  Without  it  the  temperature  of  the 
body  would  quickly  fall  to  that  of  the  air  about  it,  and 
this  would  be  fatal  to  the  cells ;  for,  as  you  already 
know,  the  cells  can  live  and  be  in  health  only  when  the 
temperature  of  the  body  is  close  to  98  degrees  (page  83). 

Food  as  building  material.  The  human  body  is  more 
wonderful  than  any  machine  made  by  man  in  that  it 
builds  its  own  parts  and  keeps  them  in  repair.  The 
body  starts  as  a  single  cell,  which  is  composed  of 
protoplasm,  or  living  material.  This  cell  builds  more 
protoplasm,  increases  in  size,  and  divides,  and  this 
process  is  kept  up  until  the  full-grown  body  is  finally 
built  of  living  cells  which  have  come  from  the  first  cell. 
Even  after  the  body  is  grown,  new  cells  must  be  built ; 
for  as  long  as  life  continues,  the  outer  cells  of  the  skin, 
the  red  blood  corpuscles,  and  some  of  the  other  cells  are 
dying  and  being  replaced  by  new  cells. 

New  protoplasm  is  also  constantly  needed  to  repair  the 
cells ;  for  within  all  the  cells  the  living  protoplasm  is 
constantly  breaking  down  and  new  protoplasm  is  being 
built  to  take  its  place.  The  material  that  is  used  in  all 
this  building  of  living  matter  comes  from  the  food  that 
we  eat.  Food  is  necessary  to  furnish  material  for  the 
growth  and  repair  of  the  cells. 

Elements  found  in  the  body.  The  living  matter  of  the 
body  is  composed  of  at  least  five  different  elements, 
all  built  together  into  a  material  that  is  very  different 
from  any  of  them.  The  black  solid  called  carbon 
makes  up  over  one  half  of  the  whole.  The  two  gases 
of  the  air,  oxygen  and  nitrogen,  together  with  another 


138  PRIMER    OF  PHYSIOLOGY 

very  light  and  highly  explosive  gas,  called  hydrogen, 
make  up  nearly  all  the  remainder.  In  addition,  some 
sulfur  is  built  into  protoplasm,  and  in  the  nucleus  of 
the  cell  a  little  phosphorus  is  found.  Among  other 
elements  that  are  present  in  the  body  are  chlorin  and 
five  minerals,  —  potassium,  sodium,  calcium,  magnesium, 
and  iron.  It  is  not  intended  that  you  shall  remember 
the  names  of  all  these  elements,  but  it  is  intended  that 
you  shall  understand  that  the  body  is  made  of  perfectly 
definite  materials,  and  that  if  these  materials  are  not 
supplied  in  our  foods,  the  body  must  suffer. 

The  three  classes  of  foods.  Foods  are  divided  into 
three  classes,  according  to  the  elements  of  which  they 
are  composed.  These  classes  are  the  proteins,  the 
carbohydrates,  which  include  the  starches  and  sugars, 
and  the  fats.  Lean  meats,  eggs,  milk,  peas,  beans, 
and  all  foods  made  from  grains  are  rich  in  protein. 
Potatoes,  turnips,  cabbage,  and  other  vegetables  are 
valuable  mainly  for  their  starch.  Grains  also  contain 
large  amounts  of  starch.  Fruits,  sweet  potatoes,  honey, 
molasses,  and  milk  contain  sugar,  and  we  add  great 
quantities  of  sugar  to  our  foods  to  make  it  more 
pleasant  to  the  taste.  Fats  and  oils  we  get  in  butter, 
lard,  fat  meat,  eggs,  cheese,  chocolate,  nuts,  and  olive 
and  cottonseed  oil.  In  general,  we  get  proteins  and 
fats  from  animals,  while  from  plants  we  get  proteins 
and  carbohydrates.  From  the  table  on  page  244  you 
can  learn  the  relative  amounts  of  carbohydrates,  fats, 
and  proteins  in  different  foods. 

Proteins  the  building  foods.  All  three  classes  of  foods 
give  heat  and  strength  to  the  body.  The  proteins  fur- 
nish building  materials  in  addition.  They  contain  the 


FOODS  AND    WHY  WE  NEED    THEM          139 

same  five  elements  that  are  found  in  the  living  matter 
of  the  body,  —  carbon,  hydrogen,  oxygen,  nitrogen,  and 
sulfur.  Since  they  are  used  for  building  up  the  cells, 
we  should  expect  them  to  contain  these  elements ;  for 
we  use  leather  to  patch  a  leather  shoe,  steel  to  replace 
a  worn-out  part  in  a  machine,  and  to  repair  the  body, 
the  materials  of  which  the  body  is  built  must  be  used. 

Minerals  necessary  to  the  body.     A  man  excretes  from 
his  body  nearly  an  ounce  of  mineral  salts  daily,1  and  it  is 


FIG.   no.      Wild   animals   often  travel   long  distances  to  salt-licks.      Man 
supplies  himself  with  salt,  but  he  often  lacks  other  minerals. 

necessary  that  certain  amounts  of  the  different  minerals 
found  in  the  body  be  supplied  to  make  good  this  loss. 
In  our  food  we  always  get  small  quantities  of  these  min- 
erals, and  little  attention  has  been  given  to  making  sure 
that  diets  include  a  sufficient  supply  of  them.  Recent 
experiments  show  that  this  trusting  to  chance  for  the 
right  amount  of  minerals  is  not  always  satisfactory. 
Not  counting  common  salt,  with  which  we  all  supply 
ourselves,  the  three  minerals  that  may  be  lacking  in  our 

1  The  greater  part  of  this  mineral  matter  is  common  salt,  of  which  the 
average  man  uses  daily  from  one  third  to  two  thirds  of  an  ounce.  This 
is  more  than  is  necessary  for  the  health,  for  experiments  indicate  that  one 
tenth  of  this  amount  is  sufficient  to  keep  the  body  in  good  condition. 


140  PRIMER   OF  PHYSIOLOGY 

food  are  iron,  calcium  (lime),  and  phosphorus.  We 
shall  discuss  the  need  for  each  of  these  separately. 

Iron  needed  to  build  red  blood  corpuscles.  Iron  is  used 
in  the  body  mainly  in  building  hemoglobin,  the  sub- 
stance in  the  red  blood  corpuscles  that  carries  the  oxy- 
gen. If  the  supply  of  iron  falls  too  low,  the  person 
becomes  pale  and  weak  because  of  a  lack  of  red  cor- 
puscles and  because  of  a  lack  of  hemoglobin  in  the  cor- 
puscles that  he  has.  In  cases  of  this  kind  the  patient 
is  given  iron  in  liquid  form  as  a  medicine,  and  a  little  of 
this  seems  to  be  used  by  the  body ;  but  all  physicians 
agree  that  for  building  hemoglobin  the  iron  in  food  is 
far  more  valuable  than  iron  in  other  forms. 

The  green  parts  of  vegetables,  especially  spinach,  are 
rich  in  iron;  and,  in  general,  eggs,  vegetables,  and  grains, 
when  the  outer  portion  of  the  grain  is  used,  give  a  rich 
supply  of  this  mineral.  Milk  is  low  in  iron,  and  in  ani- 
mals that  feed  their  young  on  milk  a  large  surplus  store 
of  iron  is  laid  up  in  the  .body  before  birth.  It  is  esti- 
mated that  fifteen  milligrams  of  iron  are  needed  daily  by 
a  healthy  man,  and  that  the  average  diet  contains  from 
twelve  to  nineteen  milligrams.1  This  indicates  that  it 
would  be  very  easy  to  select  a  diet  that  would  be  defi- 
cient in  this  important  mineral. 

Lime  needed  by  the  body.  Careful  investigation 
has  shown  that  growing  animals  require  about  1.2  per 
cent  as  much  calcium  as  they  gain  in  weight.  When 
this  amount  of  calcium  is  not  provided,  the  bones  are 
frail  and  the  teeth  are  soft  and  defective.  There  must 
also  be  a  certain  amount  of  calcium  dissolved  in  the 

1  An  ounce  of  iron  would  furnish  the  body  with  15  milligrams  a  day  for 
five  years. 


FOODS  AND    WHY  WE  NEED   THEM  141 

fymph  to  keep  the  cells  in  health,  and  if  the  supply  of 
lime  be  cut  off  entirely,  life  cannot  continue.  It  is 
claimed  that  one  half  the  people  of  the  United  States 
are  suffering  from  lime  starvation,  and  it  is  certainly 
true  that  many  young  children  are  not  supplied  with 
enough  of  this  mineral.  Adding  a  little  limewater  to 
artificial  foods  does  not  provide  enough  lime  to  be  of 
much  importance  in  building  the  skeleton  and  the 
teeth ;  for  a  pint  of  limewater  as  strong  as  it  can  be 
made  contains  slightly  less  lime  than  is  contained  in  a 
pint  of  cow's  milk.  Milk,  eggs,  vegetables  (especially 
leaf  vegetables),  and  whole  grains  hold  the  first  place 
among  the  foods  that  are  rich  in  lime  (page  244). 

Lack  of  phosphorus  in  the  body.  Experiments  indicate 
that  from  65  to  90  milligrams  of  phosphorus  are  needed 
daily  in  the  body,  —  an  amount  greater  than  many  diets 
will  supply.  The  yolk  of  egg,  the  outer  layer  of  grains, 
peas,  beans,  chocolate,  and  nuts  are  especially  rich  in 
phosphorus.  Meats  also  supply  considerable  quantities 
of  this  element  to  the  body.  Larger  amounts  of  phos- 
phorus are  needed  during  the  growing  period  than  in 
adult  life,  and  if  this  is  not  supplied  the  bones  are  likely 
to  become  soft. 

Foods  rich  in  minerals.  It  is  perhaps  worth  while  to 
call  attention  at  this  time  to  the  fact  that  the  foods  on 
which  young  animals  live  while  starting  in  the  world 
supply  minerals  as  well  as  protein  and  energy-yielding 
substances  to  the  body.  Milk  has  in  it  all  the  elements, 
except  iron,  that  are  necessary  to  nourish  a  young  animal, 
and  an  egg  has  in  it  everything  necessary  to  build  a 
chick,  including  the  iron  for  the  blood  corpuscles  and 
the  lime  for  the  skeleton. 


142 


PRIMER  OF  PHYSIOLOGY 


Foods  which  are  rich  in  minerals  ought  to  form  a 
great  part  of  our  diet  and  be  eaten  by  young  people 
especially.  Vegetables,  also,  because  of  the  large  quan- 
tities of  them  that  can  be  eaten,  furnish  a  rich  supply 
of  minerals  to  the  body.  In  the  body  of  an  animal  the 
lime  is  in  the  skeleton,  and  when  we  eat  the  meat  we 


FIGS,  ni  and   112.     Eggs  and  milk    contain  all  the 
elements  necessary  to  start  a  young  animal  on  its  life. 

get  little  of  this  mineral.1  In  wheat  the  mineral  mat- 
ter is  mainly 'near  the  surface  of  the  grains  and  is  not 
found  in  white  flour.2  A  diet,  therefore,  that  is  com- 
posed chiefly  of  meat  and  white  bread  is  low  in  the 
minerals  needed  by  the  body.  Whole  wheat  bread, 
oatmeal,  breakfast  foods,  and,  in  general,  vegetables 
and  fruits,  are  rich  in  minerals.  Children  who  are  fed 
too  long  on  milk  suffer  because  of  a  lack  of  iron,  and 
a  meat  diet  supplies  less  mineral  to  the  body  than  a 
vegetable  diet.  The  diet  of  children  in  particular  needs 

1  When  a  wolf  or  a  fox  eats  a  bird  or  a  hare,  it  makes  sure  of  a  supply 
of  calcium  for  itself  by  eating  the  bones  as  well  as  the  flesh.     Puppies  fed 
only  on  lean  meat  and  fat  meat  showed   weakness  of  the  bones,    while 
other  puppies  of  the  same  litter  that  were   given  bones  to  gnaw,  in  addi 
tion  to  the  meat,  developed  normally. 

2  The  laxative  effect  of  whole  wheat  bread  is  now  believed  to  be  due 
to  the  rich  supply  of  phosphorus  in  it,  and  not  to  the  irritating  effects  of 
the  bran,  as  was  formerly  supposed, 


FOODS  AND  WHY  WE  NEED  THEM    143 

care  to  make  sure  that  the  right  minerals  are  contained 
in  it,  for  there  is  a  special  need  for  mineral  matter  when 
the  body  is  growing  rapidly.  Generally  speaking,  the 
mineral  income  of  the  body  can  be  increased  by  cutting 
down  the  amounts  of  meat  and  white  bread  eaten  and 
using  milk  and  vegetables  more  freely. 

Vitamins.  Within  the  last  few  years  it  has  been  dis- 
covered that  certain  substances  called  vitamins  are 
necessary  for  health.  We  do  not  know  exactly  what 
vitamins  are,  but  small  amounts  of  them  are  found  in 
our  foods,  and  a  good  diet  must  contain  them.  They 
are  destroyed  by  cooking  with  alkalis,  and  are  therefore 
not  found  in  corn  bread  or  in  biscuit  made  with  soda. 

We  are  not  sure  how  many  vitamins  there  are,  but 
two  are  definitely  known  to  exist.  One  is  present  in 
whole  grains,  in  beans,  peas,  potatoes,  turnips,  and  other 
vegetables,  and  in  milk  and  eggs.  In  our  country  almost 
every  one  secures  enough  of  this  vitamin,  but  the  lack  of 
it  causes  a  disease  of  the  nervous  system  called  beriberi, 
which  is  responsible  for  many  deaths  among  peoples 
who  live  chiefly  on  rice.  The  second  vitamin  is  found 
in  milk  and  butter,  the  yolk  of  eggs,  and  the  green  parts 
of  vegetables.  When  animals  are  given  a  diet  that  con- 
tains none  of  this  vitamin,  growth  does  not  take  place 
and  there  is  soreness  of  the  eyes ;  and  when  the  supply 
of  vitamin  is  low,  growth  is  slow  and  the  health  is  poor. 
Many  persons  in  our  country  do  not  get  enough  of  this 
vitamin,  and  one  of  the  chief  reasons  for  the  use  of  leaf 
vegetables  and  milk  is  to  secure  an  abundant  supply  of 
it. 

Selecting  foods.  Of  all  the  hygienic  problems  that 
confront  mankind,  that  of  selecting  a  proper  diet  is  one 


144  PRIMER    OF  PHYSIOLOGY 

of  the  most  difficult.  Since  the  health  of  the  digestive 
organs  must  be  kept  in  mind  as  well  as  the  needs  of  the 
body  for  certain  materials,  the  whole  subject  can  be 
entered  into  more  intelligently  after  the  digestive  system 
has  been  studied.  In  the  next  chapter,  therefore,  we 
shall  discuss  the  digestive  organs  and  their  work,  and 
shall  then  take  up  the  more  difficult  subject  of  selecting 
a  diet  that  will  keep  the  human  body  in  health. 

QUESTIONS 

Give  three  uses  of  foods  in  the  body.  Name  the  five  ele- 
ments that  make  up  most  of  the  body  tissues.  Name  some 
other  elements  which  are  present  in  the  body.  Name  the 
three  classes  of  foods.  What  foods  are  rich  in  protein  ?  in 
starch  ?  in  sugar  ?  in  fat  ? 

Which  classes  of  foods  give  heat  and  strength  to  the  body  ? 
Which  class  furnishes  building  material  ? 

For  what  is  iron  used  in  the  body  ?  In  what  foods  is  iron 
abundant  ?  Why  is  lime  necessary  to  the  body  ?•  What  foods 
are  rich  in  lime  ?  What  foods  are  rich  in  phosphorus  ? 
Why  are  milk  and  eggs  complete  foods  ?  Why  is  a  diet  of 
meat  and  white  bread  deficient  in  minerals  ? 

What  are  vitamins  ?  What  diseases  are  due  to  a  lack  of 
them  ?  In  what  foods  is  each  vitamin  found  ? 

SUGGESTIONS  TO   THE  TEACHER 

Sherman's  Chemistry  of  Food  and  Nutrition  (Macmillan)  gives 
tables  of  food  analyses,  an  excellent  general  treatment  of  nutrition, 
and  a  particularly  full  treatment  of  the  mineral  constituents  of  the 
diet.  McCollum's  The  Newer  Knowledge  of  Nutrition  (Macmillan) 
is  a  new  book  treating  the  subject  from  a  very  practical  point  of 
view. 


CHAPTER   SIXTEEN 

THE  DIGESTIVE  ORGANS  AND    THEIR  WORK 

ROBINSON  CRUSOE  on  his  island  had  plenty  of  goats, 
and  from  goat  hair  a  fine  waterproof  cloth  is  woven 
that  is  used  as  a  covering  for  the  tops  of  automobiles. 
Yet,  because  Crusoe  had  no  way  of  turning  the  hair  of 
his  goats  into  cloth,  he  was  forced  to  wear  clothes  made 
of  stiff,  heavy  skins  and  to  carry  an  absurdly  heavy  and 
awkward  skin  umbrella.  There  were  trees  in  abun- 
dance on  the  island,  but  it  required  much  labor  to  con- 
vert them  into  baskets,  furniture,  and  boats.  There  was 
clay  from  which  all  kinds  of  dishes  and  vessels  could 
have  been  made,  but  he  went  for  years  without  tasting 
soup  or  boiled  food,  and  he  counted  it  one  of  the  happy 
hours  of  his  life  when  he  succeeded  in  making  a  rude 
vessel  that  would  stand  the  fire.  There  were  tons  of 
sand  to  be  had  from  which  glass  might  easily  have  been 
manufactured,  but  he  had  no  windows  in  his  dwellings. 
All  about  Crusoe  were  materials  from  which  a  thousand 
articles  could  have  been  made  that  would  have  added 
to  his  comfort  and  enjoyment,  but  until  these  materials 
were  worked  over  and  changed,  he  could  not  put  them 
to  use. 

The  meats,  grains,  and  vegetables  that  we  eat  contain 
the  materials  that  are  needed  for  the  nourishment  of 
our  bodies,  but  the  form  of  these  foodstuffs  must  be 
changed  before  we  can  use  them.  As  ice  must  be  melted 
before  the  elements  that  are  in  it  can  be  used  by  the 
body,  so  must  our  foods  be  digested  before  they  can  be 
taken  into  the  blood  and  used  by  the  cells.  Digestion 
is  the  process  of  breaking  up  nnd  changing  our  foods  into 


146 


PRIMER   OF  PHYSIOLOGY 


substances  that  can  be  dissolved  and  taken  into  the  blood. 

Until  this  is  done,  our  solid  food  is  as  useless  to  us  as 

were  most  of  the  materials  on  his  island  to  Robinson 

Crusoe. 

The  digestive  system.     The  digestive  system  includes 

the  alimentary  canal,  the  teeth,  the  salivary  glands,  the 

liver,  and  the  pan- 
creas. The  ali- 
mentary canal  is 
the  long  passage- 
way through  the 
body  into  which 
the  food  is  taken 
and  in  which  it 
stays  while  it  is 
being  digested. 
It  is  lined  with  a 
smooth  mucous 
membrane,  and  in 
its  walls  are  mus- 
cles to  force  the 
food  onward 

intestine      througn       the 

canal.  The  teeth 
are  a  mill  set  at 
the  mouth  of  the 
alimentary  canal 
to  crush  and  grind  the  food  into  small  pieces  so  that  it 
will  be  easier  to  digest.  The  other  digestive  organs  are 
glands  that  pour  juices  into  the  alimentary  canal  to 
assist  in  the  digestion  of  the  food.  The  whole  process 
of  preparing  the  food  for  the  use  of  the  body  is  a  most 


large 
intestine 


vermiform 
appendix 

FIG.  113. 


The  digestive  system. 


THE  DIGESTIVE  ORGANS  AND   THEIR    WORK     147 


important  one,  and  the  great  set  of  organs  that  carry 
it  on  fill  nearly  the  whole  abdominal  cavity. 

The  digestive  glands.  The  digestive  glands  are 
formed  by  the  folding  of  the  mucous  membrane  that 
lines  the  alimentary  canal 
into  deep  little  pockets. 
The  juices  that  digest  the 
food  flow  out  of  the  mouths 
of  these  glands.  The 
liquid  part  of  the  juices 
is  composed  of  water  that 
passes  through  the  walls 
of  the  glands  from  the 
lymph,  as  water  passes 
into  a  sweat  gland  (page 
85).  Some  glands  are 
simple,  like  little  wells 
sunk  in  the  walls  of  the 
digestive  tract.  Others,  FlG'  II4'  Diagram  of  a  simple  gland" 
like  the  salivary  glands  and  the  pancreas,  are  branched 
like  a  tree,  and  the  juices  that  come  from  them  are  se- 
creted by  hundreds  of  little  tubules,  all  of  which  flow 
into  the  main  duct  of  the  gland.-  The  glands  are  said 
to  secrete  when  the  liquid  flows  from  them,  and  the  liquid 
itself  is  called  the  secretion  of  the  gland. 

The  work  of  digestion  done  by  enzymes.  Dissolved 
in  the  secretions  of  the  digestive  glands  are  certain 
substances  called  enzymes.  These  are  built  up  by  the 
cells  that  compose  the  walls  of  the  glands  and  are  dis- 
solved by  the  liquid  which  passes  through  the  cells 
when  the  glands  secrete.  The  work  of  digesting  the 
foods  is  done  by  the  enzymes.  An  enzyme  digests  only 


artery 


148 


PRIMER   OF  PHYSIOLOGY 


one  kind  of  food,  so  there  are  different  enzymes  secreted 
for  breaking  up  the  protein,  fat,  starch,  and  each  of  the 
different  kinds  of  sugars  that  we  eat.  As  we  study  the 
work  of  the  different  digestive  juices,  we  shall  speak  of 
them  as  digesting  the  foods.  You  will  understand,  how- 
ever, that  it  is  the  enzymes  in  these  juices  that  do  the 
actual  work  of  digestion. 

The  salivary  glands.  There  are  three  pairs  of  sali- 
vary glands.  One  pair  lies  under  the  tongue ;  one 
pair  is  found  under  the 
corners  of  the  lower 
jaw ;  and  the  other  pair 
is  found  in  front  of 
and  below  the  ears 
(Fig.  115).  These  glands 
secrete  the  saliva,  which 
is  carried  to  the  mouth 
by  ducts  'leading  from 
the  glands.  The  saliva 
moistens  the  food  and 

makes  it  possible  to  swallow  food  like  crackers,  which 
in  a  dry  state  would  become  dust  in  the  mouth. 
Dissolved  in  the  saliva  is  an  enzyme  which  begins  the 
process  of  digestion  by  attacking  the  starch  that  is  in 
the  food  and  breaking  it  up  into  malt  sugar. 

The  esophagus  and  stomach.  The  esophagus  is  the 
tube  connecting  the  throat  and  the  stomach.  Food  and 
drink  do  not  fall  down  the  esophagus,  but  are  forced 
down  it  by  the  contraction  of  the  muscles  in  the  walls 
of  the  esophagus.  This  you  can  prove  by  drinking 
with  your  head  lower  than  your  body. 

The  stomach  stands  almost  on  its  end  on  the  left  side 


FIG.  115.    Tne  salivary  glands. 


THE  DIGESTIVE  ORGANS  AND   THEIR    WORK     149 

of  the  body  close  up  under  the  diaphragm.  It  holds 
about  three  pints,  and  when  full  is  about  a  foot  long. 
When  empty,  its  walls  are  drawn  together  and  it 
occupies  little  space.  It  has  a  double  function  —  to 
serve  as  a  storehouse  for  food  so  that  enough  can  be 
eaten  at  one  time  to  supply  the  body  for  several  hours, 
and  to  secrete  gastric  juice  for  the  digestion  of  the  food. 

The  gastric  juice.  From  two  and  one  half  to  five 
quarts  of  gastric  juice  are  secreted  a  day.  It  comes 
from  the  many  hundreds  of  little  glands  which  lie  in  the 
stomach  wall  and  open  into  the  stomach.  The  gastric 
juice  contains  an  enzyme  called  pepsin  that  digests 
protein.  It  contains  also  an  acid  which  kills  many  of 
the  bacteria  in  the  foods  and  so  keeps  these  bacteria 
from  causing  trouble  in  the  intestine.  The  acid  in  the 
gastric  juice  stops  the  action  of  the  saliva  •  on  the 
starch,  but  in  the  upper  part  of  the  stomach  the  food 
may  lie  from  one  to  two  hours  before  the  gastric  juice 
works  its  way  through  it.  The  saliva,  therefore,  has  a 
considerable  time  in  which  to  digest  the  starch  before 
the  acid  reaches  it.  The  heat  in  the  stomach  melts  the 
fat  in  the  food,  which  assists  in  reducing  the  whole 
food  mass  to  a  liquid  condition. 

The  small  intestine.  The  small  intestine  is  coiled 
and  folded  upon  itself  in  the  abdominal  cavity.  It  is 
about  twenty-two  feet  in  length  and  its  walls  are  lined 
with  thousands  of  little  glands.  These  glands  secrete 
an  intestinal  juice  which  contains  several  enzymes  that 
are  important  in  the  digestion  of  the  food.  On  the 
intestinal  wall  are  many  little  finger-like  projections 
called  villi  (singular,  villus).  These  contain  many  blood 
vessels,  and  they  absorb  the  digested  food ;  that  is,  they 


150  PRIMER   OF  PHYSIOLOGY 

take  it  into  the  blood  through  the  intestinal  wall.  So 
abundant  are  the  villi  that  they  give  the  entire  inner 
surface  of  the  intestinal  wall  the  appearance  of  velvet. 

The  liver  and  the  pancreas.  The  liver  weighs  nearly 
four  pounds  and  is  the  largest  gland  in  the  body.  It 
lies  on  the  right  side  of  the  body  under  the  diaphragm. 
It  secretes  a  greenish  yellow  liquid  called  bile,  which 
is  poured  into  the  small  intestine  when  food  passes  into 
the  intestine  for  digestion.  The  bile  assists  in  destroy- 
ing acids  that  come  from  the  stomach,  in  making  more 
active  the  enzyme  that  digests  the  fats,  and  in  dissolv- 
ing the  fatty  foods.  In  the  next  chapter,  we  shall  study 
other  important  functions  of  the  liver. 

The  pancreas  is  a  long,  light-colored  gland  which  lies 
along  the  lower  border  of  the  stomach.  It  secretes  and 
empties  into  the  small  intestine  great  quantities  of  thin, 
watery  pancreatic  juice.  This  liquid  contains  enzymes 
for  digesting  the  three  most  important  foodstuff  s,  —  pro- 
teins, starches,  and  fats.  The  pancreatic  and  intestinal 
juices  along  with  the  bile  are  thoroughly  mixed  with  the 
food  in  the  small  intestine,  and  they  are  even  more  im- 
portant than  the  gastric  juice  in  preparing  the  food  to 
be  carried  to  all  parts  of  the  body. 

The  large  intestine.  The  large  intestine  begins  low 
down  in  the  right  side  of  the  abdominal  cavity,  passes 
up  the  right  side  of  the  body,  then  across  under  the  dia- 
phragm, and  down  the  left  side  of  the  body.  Just  below 
where  the  small  intestine  opens  into  it,  there  is  a  small, 
worm-like  structure  called  the  vermiform  appendix.  The 
walls  of  the  vermiform  appendix  contain  much  loose 
spongy  tissue  of  the  same  kind  that  is  found  in  the  ton- 
sils, and  just  as  tonsillitis  is  caused  by  germs  growing  in 


THE  DIGESTIVE  ORGANS  AND   THEIR    WORK     151 

the  tonsils,  so  appendicitis  is  caused  by  germs  growing 
in  the  walls  of  the  appendix. 


the  food  masticated  and  mixed  with 
saliva 


starch  digested  by  the  saliva 

food  mixed  with  gastric  juice ;  pepsin 
digests  proteins;  fats  melted  and 
food  liquefied 

food  mixed  with  bile,  pancreatic  juice^ 
and  intestinal  juice  ;  pancreatic  juice 
digests  proteins,  starches,  and  fats; 
sugars  digested  to  grape  sugar  by  en- 
zymes in  intestinal  juice 

food  continually  cut  into  segments  and 
mixed  with  digestive  juices;  digestion 
goes  on,  and  digested  food  absorbed 
and  carried  away;  a  few  bacteria 
present  in  refuse 

liquids  being  absorbed;  mucus  and 
wastes  excreted  by  glands ;  abundant 
growth  of  bacteria 

continued  growth  of  bacteria;  wastes 
contain  poisonous  siibstances  and 
should  be  removed  from  the  body  to 
prevent  the  poisons  from  being  ab- 
sorbed into  the  blood 


FIG.  116.     A  diagram  illustrating  the  changes  that  take  place  in  the  food  during 
its  journey  through  the  different  parts  of  the  alimentary  canal. 

The  story  of  digestion.  Let  us  now  trace  the  history 
of  a  meal  by  imagining  that  we  can  see  the  food  after  it 
has  been  eaten,  and  that  we  can  watch  it  while  it  is  being 
digested.  In  the  mouth  we  find  that  the  teeth  slide  over 


152  PRIMER   OF  PHYSIOLOGY 

each  other,  crush  the  food  into  small  pieces,  and  mix  it 
with  saliva.  The  enzyme  in  the  saliva  at  once  begins 
the  process  of  digestion  by  attacking  the  starch  that  is 
in  bread,  potatoes,  and  many  other  of  our  foods,  and 
changing  it  to  sugar. 

After  the  food  has  been  chewed,  the  tongue  draws  it 
back  into  the  opening  of  the  pharynx.  The  walls  of  the 
pharynx  then  grasp  it  and  press  it  backward  and  down- 
ward into  the  esophagus,  through  which  it  is  carried  to 
the  stomach.  When  the  food  reaches  the  stomach,  the 
gastric  juice  trickles  in  on  it  from  the  glands  in  the  walls 
all  about,  and  the  pepsin  attacks  the  meats  and  other  pro- 
tein foods.  Under  the  action  of  the  gastric  juice  the  outer 
layer  of  the  food  mass  dissolves  and  slides  on  into  the 
lower  part  of  the  stomach,  where  the  stomach  walls  con- 
tract on  it  and  squeeze  it  about  to  mix  the  gastric  juice 
thoroughly  with  it. 

From  time  to  time  the  ring  of  muscle  that  closes  the 
gateway  between  the  stomach  and  the  intestine  opens, 
and  a  portion  of  the  food  from  the  lower  part  of  the  stom- 
ach is  forced  on  into  the  intestine  in  the  form  of  a  thick 
liquid.1  Here  a  flood  of  digestive  juices  is  poured  in 
upon  it.  Greenish  yellow  bile  comes  from  the  liver ;  great 
quantities  of  juice  rich  in  enzymes  for  digesting  proteins, 
starches,  and  fats  are  secreted  by  the  pancreas ;  and  all 
along  the  small  intestine,  juices  containing  enzymes  are 
poured  out  by  the  thousands  of  little  glands  that  are  in 

1  It  should  be  understood  that  during  stomach  digestion  the  food  is 
continuously  being  worked  downward  from  the  upper  part  of  the  stomach, 
and  that  from  time  to  time  it  passes  on  into  the  intestine  in  rather  small 
amounts.  It  takes  about  six  hours  for  the  stomach  to  be  emptied  after 
an  ordinary  meal. 


THE  DIGESTIVE  ORGANS  AND   THEIR    WORK     153 

the  wall.  The  circular  muscles  in  the  walls  of  the  intes- 
tine keep  contracting  on  the  food  and  cutting  it  up  into 
little  sausage-like  segments  which  are  continually  being 
made,  combined,  remade,  and  moved  about,  thus  mixing 
the  digestive  juices  thoroughly  with  the  food.1  All  the 
time  the  food  is  gradually  being  worked  along  the  in- 
testine and  the  enzymes  are  bringing  about  the  following 
changes  in  it : 

The  pancreatic  juice  attacks  the  protein  and  splits  that 
which  has  escaped  the  pepsin  of  the  stomach  ;  it  breaks 
up  the  starch  and  completes  the  digestion  of  this 
part  of  the  food;  and  it  digests  the  fat,  changing 
it  into  glycerin  and  other  substances  that  will  dissolve 
in  the  intestine.  The  enzymes  in  the  intestinal  juice 
assist  in  digesting  the  protein  and  in  changing  all  the 
different  sugars  into  the  one  particular  sugar  (grape 
sugar)  that  the  body  can  use. 

And  now  as  we  follow  the  food  in  its  course  through 
the  intestine,  we  notice  that  the  liquid  becomes  less  and 
less  in  amount ;  that  only  the  solid  wastes  remain.  As 
some  desert  rivers  run  out  over  the  sand  and  lose  them- 
selves in  their  own  channels,  so  the  stream  of  liquid 
food  in  the  intestine  disappears.  Where  is  it  going? 
It  is  soaking  into  the  wall  of  the  intestine  and  passing 
into  the  millions  of  little  capillaries  that  run  in  the 
wall.  What  will  be  done  with  it?  It  will  be  car- 
ried through  all  the  body  to  furnish  heat  and  strength, 
and  to  be  built  into  bone  and  muscle  and  nerve ;  for 
as  the  waterfall,  even  though  it  keep  the  same  form, 

1  The  segments  into  which  the  food  is  cut  are  about  an  inch  long,  and 
the  contractions  of  the  muscle  rings  come  as  often  as  thirty  times  a 
minute. 


154 


PRIMER   OF  PHYSIOLOGY 


blood  vessel 


is  made  up  of  rapidly  passing  water,   so    our   bodies, 
that   seem   to   us   to    be    the    same   year  by  year,  are 

composed  of  materials  that 
are  ever  shifting.  The 
skin  that  we  have  today 
will,  in  a  short  while,  be 
dead  and  gone,  and  the 
food  that  we  eat  today 
will  be  built  into  a  new 
skin.  The  flesh  and  heart 
and  brain  of  an  ox  are 
built  of  grass,  and  the 


intestine 

FlG.  117.    Showing  the   vessels  which 


carry  the  food  from  the  small  intestine. 


human  body  is  built  of 
the  food  that  we  eat. 

The  refuse  matter  in  the  large  intestine.  In  all  food 
there  is  some  indigestible  material  likfe  the  woody, 
fibrous  parts  of  potatoes  and  cabbages,  the  skins  of 
fruits,  and  the  tough  fibers  of  meat.  This  matter  passes 
from  the  small  intestine  into  the  large  intestine,  where 
its  bulk  is  very  considerably  increased  by  mucus  and 
other  wastes  that  are  secreted  by  the  glands  in  the  wall 
of  the  large  intestine.  In  this  waste  material,  millions 
of  bacteria  grow  and  cause  decay,  and  in  the  process  of 
decay  poisonous  substances  are  formed.  Nothing  is 
more  important  to  the  health  than  that  this  refuse  ma- 
terial be  cleared  out  of  the  intestine  before  the  poisons 
are  absorbed  into  the  body.  This  question  we  shall 
discuss  in  the  next  chapter. 

Scurvy,  rickets,  and  pellagra.  The  causes  of  these 
diseases  are  not  definitely  known,  but  they  are  in  some 
way  connected  with  the  nutrition  of  the  body,  and  we 
shall  discuss  them  in  this  chapter. 


THE  DIGESTIVE  ORGANS  AND   THEIR   WORK     155 


Scurvy  is  a  disease  in  which  the  joints  are  swollen 
and  tender  and  there  is  bleeding  of  the  gums.  It  is 
found  in  infants  that 
have  been  improperly 
fed  and  among  sailors 
and  others  who  lack 
fresh  food.  It  can  be 
prevented  by  fresh 
meats  and  fresh  vege- 
tables and  fruits,  and  is 
relieved  in  a  wonderful 
way  by  orange  juice. 
Some  investigators  have 
thought  scurvy  to  be 
due  to  the  lack  of  a 
vitamin.  Others  be- 
lieve it  is  caused  by  a 
bacterium  that  is  able 
to  enter  the  body  when 
it  is  not  properly  nour- 
ished. Whatever  the 

cause,    the   disease   can  FlG-  II8-    A  milch  §oat- 

easily   be   prevented   by   proper   feeding. 

Rickets  is  a  disease  of  children  in  which  the  bones 
are  soft.  The  head  grows  larger  than  is  natural  and  be- 
comes somewhat  square,  and  there  are  knots  on  the  ribs 
on  either  side  of  the  breastbone  where  the  bone  and 
cartilage  meet.  It  has  been  suggested  that  rickets  is 
due  to  lack  of  a  vitamin  or  to  a  lack  of  calcium,  but 
neither  of  these  explanations  seems  to  be  correct.  It  is 
in  some  way  connected  with  bad  feeding  and  is  prevented 
and  benefited  by  a  properly  selected  diet. 


156  PRIMER   OF  PHYSIOLOGY 

Pellagra  is  common  in  Italy,  and  it  is  estimated  that 
in  the  United  States  there  were  165,000  cases  in  1917. 
Most  of  these  cases  are  found  in  the  Southern  states. 
The  disease  seems  to  spread  only  where  the  sanitary 
conditions  are  bad,  and  it  is  probably  caused  by  a  germ. 
At  the  same  time,  it  has  been  proved  that  it  is  brought 
on  by  a  faulty  diet  and  that  an  abundant  and  varied  diet 
with  plenty  of  fresh  foods  will  prevent  it,  even  when 
sanitary  conditions  are  bad.  It  seems  most  probable, 
therefore,  that  pellagra  is  caused  by  a  germ  that  can 
attack  the  body  only  when  it  is  in  a  weakened  condition 
because  of  improper  food. 

In  our  Southern  states  pellagra  is  a  serious  problem. 
A  great  number  of  the  persons  attacked  by  it  live,  during 
the  winter  months  especially,  chiefly  on  corn  bread,  salt 
pork,  and  molasses ;  and  it  is  very  necessary  that  milk, 
eggs,  and  fresh  vegetables  be  added  to  this  diet.  The 
garden  and  poultry  club  movements,  therefore,  deserve 
every  encouragement,  and  the  keeping  of  milch  goats 
might  go  far  toward  solving  the  diet  problem  of  many 
families.  Dried  milk,  which  seems  to  have  all  the  food 
value  of  fresh  milk,  is  now  being  prepared.  It  may  be 
that  this  will  prove  of  great  value  in  warm  regions  where 
providing  a  supply  of  fresh  milk  is  especially  difficult. 
Meats  will  not  take  the  place  of  vegetables,  eggs,  and 
milk  in  providing  minerals  and  vitamins  for  the  body 
(page  141). 

QUESTIONS 

What  change  must  be  made  in  foods  before  the  body  can 
use  them  ?  What  is  digestion  ?  Name  the  parts  of  the  digestive 
system.  Describe  the  alimentary  canal.  What  is  the  function 
of  the  teeth  ? 


THE  DIGESTIVE  ORGANS  AND  THEIR   WORK     157 

Describe  a  gland  and  explain  where  the  secretion  of  the 
gland  comes  from.  What  is  an  enzyme  ?  By  what  is  the 
work  of  digestion  done  ? 

How  many  salivary  glands  are  there  and  where  are  they  ? 
What  is  the  function  of  the  saliva  ?  What  food  is  digested  by 
the  saliva  ?  Into  what  is  it  changed  ? 

What  is  the  esophagus  ?  Describe  the  stomach.  What  is 
the  function  of  the  gastric  juice  ?  What  enzyme  does  it  con- 
tain and  what  is  the  function  of  this  enzyme  ?  How  are  the 
bacteria  killed  in  the  stomach  ? 

Describe  the  small  intestine.  What  are  villi  ?  What  is  their 
function  ?  Describe  the  liver.  What  does  it  secrete  ?  What 
is  the  use  of  the  bile  ?  Describe  the  pancreas.  What  food- 
stuffs does  the  pancreatic  juice  digest  ? 

Describe  the  large  intestine.     What  causes  appendicitis  ? 

Tell  the  story  of  the  digestion  and  absorption  of  food. 
Where  is  the  food  taken  after  it  is  absorbed  ? 

Of  what  are  the  wastes  in  the  large  intestine  composed  ? 
Why  is  it  important  that  these  wastes  be  promptly  cleared 
out  of  the  body  ? 

Name  three  diseases  that  are  due  to  an  improper  diet. 
What  foods  will  prevent  scurvy  ?  Whaf  foods  will  prevent 
pellagra  ? 

SUGGESTIONS   TO  THE  TEACHER 

Additional  information  concerning  the  structure  of  the  digestive 
organs  and  the  processes  of  digestion  may  be  found  in  Ritchie's 
Human  Physiology  (World  Book  Company,  Yonkers,  New  York). 

A  fable  by  John  W.  Ritchie  called  The  Adventures  of  the  Starch 
Family  will  be  found  helpful  in  giving  the  pupils  a  concrete  idea 
of  the  changes  undergone  by  the  foods  during  the  digestive  and 
metabolic  processes.  Application  to  the  World  Book  Company  will 
bring  a  copy  of  the  pamphlet  if  four  cents  in  stamps  is  enclosed. 

Howell's  Textbook  of  Physiology  (W.  B.  Saunders  Co.,  Philadel- 
phia) is  an  advanced  text  that  will  furnish  a  wealth  of  physiological 
information  on  almost  any  subject  discussed  in  this  book.  Lusk's 
Science  of  Nutrition  (Saunders)  gives  a  very  thorough  treatment  of 
nutrition. 


CHAPTER   SEVENTEEN 


THE  FOODS  WITHIN  THE  BODY 

WE  have  now  traced  the  food  through  its  digestion. 
We  have  explained  how  it  is  taken  into  the  blood  and 

carried  to  the  cells. 
What  do  the  cells 
do  with  it  ?  WThat 
becomes  of  it  after 
the  cells  have  fin- 
ished with  it? 
Why,  when  we 
keep  eating  all  the 
time,  does  not  the 
body  become  so 
full  of  food  that 
we  cannot  take  in 

FIG.  119.    When  the  candle  burns  tne  elements  in    more?     Perhaps  it 
it  are  not  destroyed.  mav    start    you    to 

thinking  about  this  subject  in  the  right  way  if  we  go 
back  for  a  few  minutes  to  something  else  that  you  have 
seen. 

Long  ago  in  your  Mother  Goose  book  you  read : 

"  Little  Nanny  Etticoat, 
In  a  white  petticoat 
And  a  red  nose. 
The  longer  she  stands, 
The  shorter  she  grows." 

Why  does  a  lighted  candle  grow  shorter  the  longer 
it  stands?  What  becomes  of  the  candle  when  it  is 
burned  ?  You  must  study  chemistry  before  you  will 
have  a  really  clear  idea  of  what  happens  in  the  process 
of  burning.  At  present  we  can  only  explain  to  you 

158 


THE  FOODS   WITHIN  THE  BODY  159 

that  the  oxygen  of  the  air  unites  with  the  elements  of 
which  the  wax  is  composed  and  forms  carbon  dioxid 
and  water,  which  pass  off  into  the  air.  The  materials 
in  the  candle,  therefore,  are  not  destroyed.  They  are 
merely  changed  to  vapor  and  gas. 

The  fate  of  the  carbohydrates  and  the  fats.  The 
cells  of  the  body  take  in  the  sugar  and  fats  of  the 
foods.  They  also  take  in  oxygen.  Within  the  cells  the 
oxygen  and  the  food  unite  slowly  and  without  smoke 
or  flame,  and  the  food  is  oxidized,  or  burned  as  truly 
as  the  wax  of  a  lighted  candle  is  burned.  This  oxida- 
tion of  the  foods  furnishes  heat  to  the  body  and  strength 
to  the  muscle  cells ;  and,  as  in  the  burning  of  the  candle 
the  wax  is  changed  to  carbon  dioxid  and  water,  so 
within  the  cells  the  fats  and  carbohydrates  are  changed 
4to  carbon  dioxid  and  water.  The  carbon  dioxid  is 
breathed  out  of  the  body  through  the  lungs.  The 
water  is  excreted  by  the  lungs,  the  kidneys,  and  the 
skin.  Thus  the  fuel  foods  are  burned  in  the  cells  and 
the  wastes  which  are  formed  from  them  are  cast  out  of 
the  body.  The  profit  which  the  body  receives  from  these 
foods  is  the  heat  and  the  power  to  do  work  which  are 
given  to  the  body  when  they  are  burned. 

The  fate  of  the  protein  foods  in  the  body.  The  living 
protoplasm  of  the  body  is  continually  breaking  down 
and  being  oxidized.  The  protein  food  is  used  to  build 
new  protoplasm  to  take  the  place  of  that  which  is 
broken  down.1  In  time  this  protoplasm  will  also  be 
broken  down  and  oxidized,  so  that  the  proteins  are  as 

1  It  should  be  understood  that  only  a  part  of  protein  food  is  built  into 
living  tissue.  Surplus  protein  and  even  part  of  the  protein  that  seems  to 
be  necessary  for  life  is  oxidized  as  described  on  page  162. 


i6o 


PRIMER   OF  PHYSIOLOGY 


truly  burned  in  the  body  as  are  the  carbohydrates  and 
fats.  The  difference  is  that  they  are  built  into  living 
material  before  the  oxidation  takes  place.  Carbon  di- 
oxid  and  water  are  among  the  waste  products  that 
come  from  the  burning  of  the  proteins,  but  there  are 
other  wastes  also,  —  uric  acid  and  other  similar  sub- 
stances. These  wastes  are  in- 
jurious to  the  cells,  and  the 
liver  does  a  very  important 
work  in  gathering  up  and  con- 
verting a  great  part  of  them 
into  urea,  which  is  excreted 
from  the  body.1  We  shall  now 
describe  the  organs  that  elimi- 
nate the  protein  wastes. 

The  kidneys.  Fastened  to 
the  back  wall  of  the  abdomi- 
nal cavity  are  two  bean-shaped 
organs,  called  the  kidneys. 
Each  kidney  has  in  it  many 
thousands  of  little  tubes  which 
all  drain  into  a  larger  tube,  the 
ureter  (Fig.  120).  The  little 

FlG.  120.    The  kidneys  and  the     ,    -,          .  ,  .  -,  1M        ,, 

bladder  seen  from  behind.  tubes   m    the   kidneys,    like  the 

sweat  glands,  are  surrounded 

by   lymph,    and  the   water   of  the  lymph   passes  into 
them  and  flows  out  of  their  mouths,  as  water  passes 

1  About  92.5  per  cent  of  all  the  protein  wastes  excreted  by  the  kidneys 
is  in  the  form  of  urea.  About  2  per  cent  of  the  whole  is  excreted  in  the 
form  of  uric  acid,  and  it  is  estimated  that  an  equal  amount  of  uric  acid  is 
converted  into  urea  by  the  liver.  The  uric  acid  part  of  the  wastes  comes 
from  the  nuclei  of  the  cells  and  from  the  muscle  cells  when  they  work. 


THE  FOODS   WITHIN  THE  BODY  i6l 

into  a  sweat  gland  and  flows  out  on  the  skin.  The 
urea  and  other  protein  wastes  are  dissolved  in  the  lymph, 
and  they  leave  the  body  by  passing  with  the  water 
through  the  kidney  tubes  into  the  ureter  and  draining 
off  to  the  bladder.  The  function  of  the  kidneys  is  to 
excrete  water,  salts,  and  protein  wastes. 

Storage  of  the  foods  within  the  body.  When  more 
carbohydrate  is  eaten  than  is  needed  for  immediate  use 
in  the  body,  it  is  changed  to  a  starch-like  substance 
called  glycogen,  and  is  stored  within  the  cells  of  the 
liver  and  to  a  certain  extent  in  the  fibers  of  the 
muscles.  When  the  supply  of  sugar  in  the  blood  runs 
low,  this  reserve  store  of  glycogen  is  broken  up  again 
into  sugar  and  given  off  into  the  blood  to  feed  the  cells. 

When  more  fat  is  eaten  than  can  be  used  in  the  body, 
certain  cells  take  it  in  and  store  it  within  themselves 
until  they  become  little  more  than 
bags  of  oil.  These  cells,  massed 
together,  form  the  fat  that  you  see 
in  the  body  of  an  animal.  When 
a  person  is  sick  and  does  not  eat, 
the  body  uses  this  fat  for  food. 

A  small  amount  of  protein  is  dis- 
solved in  the  blood,  but  the  great 
storehouse  of  the  protein  in  the 
body  is  the  muscles.  The  muscles 
are  built  up  when  we  eat  a  diet  that 
is  rich  in  protein,  and  when  for  any  FIG.  121.  Fat  ceils.  They 
reason  we  are  deprived  of  food,  the  are  little  more  than  bags  of 
muscle  fibers  are  broken  down  and 

used  to  nourish  the  cells  of  the  heart,  the  brain,  and 
other  vital  organs.  Famine  sufferers  and  persons  who 


162  PRIMER   OF  PHYSIOLOGY 

have  come  through  long  sicknesses  are  little  more  than 
skeletons  because  their  muscles  have  been  used  to  sus- 
tain the  organs  necessary  for  life  and  the  fat  has  been 
used  to  give  the  body  heat  and  strength. 

Surplus  food  in  the  body.  When  we  eat  more  carbo- 
hydrate than  can  be  stored  in  the  liver  and  muscles,  it 
is  converted  into  fat  and  stored  in  this  form.  Usually 
we  lose  our  appetite  for  carbohydrates  and  fats  when 
we  have  had  enough  to  furnish  a  reasonable  supply  of 
fat  in  the  body.  We  can,  therefore,  in  most  cases  trust 
our  appetites  to  tell  us  when  we  have  had  enough  bread, 
potatoes,  fat  meat,  butter,  or  other  starchy  or  fatty  foods 
(page  175).  There  are,  however,  a  few  persons  whose 
cells  oxidize  these  foods  very  slowly,  and  such  persons 
become  too  heavy  and  fleshy  if  they  eat  freely  of  foods 
of  this  kind. 

When  more  protein  is  eaten  than  can  be  used  or 
stored  in  the  body,  it  is  broken  up,  and  excreted  through 
the  kidneys.1  From  this  protein  the  same  wastes  are 
formed  that  are  formed  from  the  breaking  down  of  the 
protein  of  the  body  cells.  A  heavy  diet  of  meat,  or  of 
other  foods  that  are  high  in  protein,  therefore,  gives  the 
liver  large  amounts  of  protein  wastes  to  change  into  urea, 
and  sometimes  more  of  these  wastes  are  thrown  into  the 
blood  than  the  kidneys  can  excrete.  This  subject  we 
shall  discuss  in  more  detail  in  the  next  chapter. 

Alcohol  as  food.     Alcohol  in  small  quantities  can  be 

1  In  the  breaking  up  of  the  excess  protein,  the  carbon  and  hydrogen  in 
it  are  converted  into  either  sugar  or  fat  and  used  to  give  the  body  heat 
and  strength.  It  is  not  to  be  understood,  therefore,  that  surplus  proteins 
are  entirely  useless  to  the  body.  The  point  is  that  they  yield  only  energy, 
and  this  can  be  obtained  much  more  cheaply  from  carbohydrates  and  fats 
without  filling  the  body  with  poisonous  wastes. 


THE  FOODS   WITHIN  THE  BODY  163 

used  to  furnish  strength  to  the  muscles.  In  quantities 
up  to  two  ounces  a  day  it  is  oxidized  within  the  cells  and 
gives  heat  to  the  body.  Because  it  can  be  used  in  these 
ways,  it  is  often  stated  that  it  is  a  food.  The  modern 
idea  of  a  food,  however,  is  that  it  must  not  only  furnish 
building  material  or  energy  to  the  body,  but  that  it  must 
also  be  harmless  when  it  is  broken  up  within  the  cells. 
This  definition  of  a  food  is,  we  think,  a  correct  one ;  for 
certainly  the  toxin  of  the  tetanus  or  the  diphtheria  germ 
is  not  a  food,  opium  is  not  a  food,  and  strychnin  is  not  a 
food.1  Yet  all  these  poisons  are  taken  into  the  cells  and 
are  broken  up  in  them,  and  they  must  furnish  a  small 
amount  of  heat  to  the  cells. 

We  cannot,  therefore,  say  that  alcohol  is  a  food  be- 
cause it  is  used  by  the  cells,  but  before  making  our 
decision  on  this  point  we  must  know  whether  in  being 
broken  up  within  the  cells  it  damages  them  —  whether 
it  interferes  with  those  wonderful  processes  that  keep 
the  protoplasm  alive.  When  we  view  the  question  in 
this  light,  we  must  decide  that  alcohol  acts  as  a  drug 
rather  than  as  a  food ;  for,  as  a  drunken  man  shows, 
the  action  of  the  mind  is  dulled  and  made  very  uncertain 
by  alcohol;  under  its  influence  the  muscles  are  weak- 

1  Alcohol  is  composed  of  carbon,  hydrogen,  and  oxygen.  It  is  made 
from  sugar,  has  in  it  the  same  elements  that  are  found  in  sugar,  and  it 
would  seem  reasonable  to  expect  it  to  act  as  a  food  toward  the  cells.  We 
must,  however,  recognize  that  not  only  what  elements  are  in  foods  and 
drugs,  but  also  the  way  they  are  built  together,  is  important  ;  for  carbolic 
acid  is  built  of  the  same  materials  and  is  closely  related  to  sugar  and 
alcohol,  and  strychnin  and  cocain  are  composed  of  carbon,  hydrogen, 
oxygen,  and  nitrogen,  —  the  same  elements  that  are  most  abundant  in 
protein  foods.  Just  why  substances  that  are  composed  of  the  same  ele- 
ments should  affect  the  cells  so  differently  is  hard  to  explain,  but  it  is  one 
of  the  facts  of  chemistry  that  we  must  accept. 


164  PRIMER   OF  PHYSIOLOGY 

ened  and  their  control  is  lost;  and  its  whole  effect 
on  the  body  is  that  of  a  drug  and  not  of  an  ordinary 
food.  Even  in  small  amounts,  —  amounts  far  too  small 
to  produce  signs  of  intoxication,  —  there  is  good  reason 
to  believe  that  alcohol  interferes  with  the  enzymes  that 
break  up  the  food  within  the  cells  and  throws  the  life 
processes  of  the  protoplasm  out  of  their  natural  course.1 

QUESTIONS 

What  becomes  of  the  materials  in  a  candle  when  the  candle 
is  burned  ?  What  happens  to  the  carbohydrates  and  fats  within 
the  cells  of  the  body  ?  What  becomes  of  the  carbon  dioxid 
that  is  formed  in  the  body?  What  becomes  of  the  water? 
What  does  the  body  gain  by  the  oxidation  of  the  fuel  foods  ? 

What  is  constantly  happening  to  the  protoplasm  of  the  body  ? 
What  happens  to  the  protein  food  before  it  is  oxidized?  What 

1  In  the  Hygienic  Laboratory  of  the  United  States  Government  at 
Washington,  an  experiment  was  performed  with  mice  and  guinea  pigs  that 
gives  reason  for  believing  that  alcohol  does  not  act  like  ordinary  foods 
within  the  cells.  In  this  experiment,  the  animals  were  given  acetonitrile, 
a  drug  that  is  not  itself  a  poison  but  which  breaks  up  into  poisonous  com- 
pounds within  the  body.  When  an  animal  was  given  along  with  the  ace- 
tonitrile the  smallest  quantities  of  alcohol,  the  acetonitrile  was  broken  up 
much  faster  than  is  natural  and  the  animal  was  poisoned  by  a  dose  too 
small  to  have  any  appreciable  effect  when  alcohol  was  not  given.  This 
proves  that  the  alcohol  changes  the  processes  that  go  on  -within  the  cells.  It 
does  ndt,  of  course,  prove  that  they  are  changed  in  a  way  that  is  injurious 
when  acetonitrile  is  not  given  with  the  alcohol,  but  there  is  a  quite  wide- 
spread belief  that  even  small  quantities  of  alcohol  have  an  evil  effect  on 
the  changes  that  *.he  protein  foods  undergo  within  the  cells.  Until  we 
know  that  this  is  not  the  case,  it  is  unreasonable  to  include  alcohol  in  our 
list  of  foods.  It  should  be  understood  that  the  above  results  followed  the 
administration  of  alcohol  in  amounts  "  far  too  small  ever  to  cause  indica- 
tions of  intoxication  and  in  doses  which  almost  certainly  cause  no  anatomi- 
cal lesions  which  could  be  detected  by  present  methods." 


THE  FOODS   WITHIN  THE  BODY  165 

wastes  are  formed  from  the  proteins  ?  Describe  the  structure 
of  a  kidney.  What  is  the  function  of  the  kidneys  ? 

How  is  carbohydrate  stored  in  the  body  ?  Under  what  con- 
ditions will  the  glycogen  be  changed  again  to  sugar  ?  How  are 
excess  sugar  and  fat  stored  in  the  body  ?  Of  what  use  is  the 
fat  in  the  body  ?  Where  in  the  body  is  protein  stored  ?  What 
happens  to  the  muscles  and  fat  of  famine  sufferers  ? 

What  happens  if  more  protein  is  eaten  than  can  be  used  or 
stored  in  the  body  ?  In  what  way  is  a  heavy  protein  diet  inju- 
rious to  the  body  ? 

Define  a  food.  Why  is  alcohol  sometimes  classed  as  a  food  ? 
What  reason  is  there  for  not  including  it  among  our  foods  ? 

SUGGESTIONS  TO  THE  TEACHER 

Review  the  reasons  why  the  body  needs  food.  Have  the  pupils 
distinguish  clearly  between  matter  and  energy.  Emphasize  the  fact 
that  except  in  the  building  foods  it  is  the  energy  and  not  the  matter 
that  is  valuable  to  the  body,  and  that  the  useless  matter  has  to  be 
thrown  out  of  the  body  as  wastes. 

The  books  referred  to  on  pages  144  and  157  give  full  accounts  of 
the  chemical  reactions  within  the  cells  and  of  the  wastes  resulting 
from  these  reactions,  and  Chittenden's  Nutrition  of  Man  (Frederick 
A.  Stokes  Company,  New  York)  treats  especially  the  question  of 
the  protein  requirements  of  the  body.  Locke's  Food  Values  (D. 
Appleton  &  Co.)  gives  in  convenient  form  the  chemical  and  energy 
values  of  average  helpings  of  prepared  foods,  and  Gephart  and  Lusk's 
Analysis  and  Cost  of  Ready-to-Serve  Foods  (Journal  American  Medi- 
cal Association,  Chicago,  price  1 5  cents)  is  of  especial  value  to  those 
who  eat  in  restaurants. 

The  teacher  should  write  to  the  Child  Health  Organization, 
156  Fifth  Avenue,  New  York  City,  for  table's  showing  the  proper 
weights  for  boys  and  for  girls  of  given  ages  and  heights.  Attention 
should  be  called  to  the  fact  that  the  weight  of  the  body  represents 
the  food  that  has  been  taken  in  by  the  body  but  not  oxidized  —  the 
excess  of  income  over  outgo  —  and  that  the  weight  can  be  increased 
or  decreased  by  regulating  the  intake  of  food. 


CHAPTER   EIGHTEEN 

FOODS   AND   HEALTH 

How  shall  we  know  what  foods  we  ought  to  eat  and 
how  much  of  each  is  best  for  us  ?  Occasionally  the  idea 
is  advanced  that  in  selecting  a  diet  the  best  plan  is  to 
follow  the  appetite,  —  that  the  lower  animals  keep  in 
health  by  eating  the  food  they  like,  and  that  when  the 
body  calls  for  anything  it  does  so  because  it  needs  it. 
It  would  be  fortunate  for  us  if  by  following  this  simple 
rule  we  could  always  be  sure  of  keeping  our  digestive 
organs  in  order  and  of  supplying  our  bodies  with  the 
materials  that  they  need.  But  as  a  matter  of  fact  this 
is  not  the  case.  Young  rats  that  were  allowed  to  eat 
freely  of  23  different  grains  and  vegetable  foods  failed 
to  grow  to  more  than  half  normal  size,  while  other  rats, 
compelled  to  live  entirely  on  a  mixture  of  rolled  oats 
and  dry  alfalfa  leaves,  reached  their  full  size.  Certainly 
many  persons  crave  foods  that  they  know  will  be  injuri- 
ous to  them,  and  in  the  selection  of  foods,  rules  and  prin- 
ciples must  be  followed  as  well  as  the  appetite,  if  the 
diet  is  to  be  adapted  to  the  body's  needs.  The  amount 
of  protein  needed  by  the  body  has  in  the  past  been  one 
of  the  most  disputed  of  all  the  questions  pertaining  to 
diet,' and  we  shall  begin  this  chapter  by  a  discussion  of 
that  question. 

Quantity  of  protein  needed  by  the  body.  When  men 
are  given  an  abundance  of  food  and  are  allowed  to  select 
the  kinds  that  they  like,  it  is  found  that  the  average  man 
consumes  daily  from  four  to  four  and  one  half  ounces 
of  dry  protein.  Some  individuals  eat  far  more  and  a 

166 


FOODS  AND  HEALTH 


I67 


few  persons  take  much  less  than  this  amount,  but  a  little 
over  four  ounces  is  the  quantity  of  protein  eaten  by  the 
average  prosperous  American  or  European. 

But  many  persons  keep  in  health  when  eating  much 
less  than  this  amount  of  protein,  and  recent  investiga- 
tions have  shown  that  proteins  differ  from  each  other 
and  that  the  amount  of  protein  needed  by  the  body 
depends  upon  the 
one  that  is  taken. 
In  digestion  the  pro- 
teins are  split  into 
amino-acids.  These 
are  absorbed  into  the 
blood  and  are  used 
as  the  building  stones 
with  which  the  body 
repairs  its  wastes  and 
grows.  Nearly  twenty 
amino-acids  are  now 
known,  which  differ- 
ent proteins  yield  in 
different  amounts; 
some  proteins  lack 

certain  amino-acids  altogether,  while  others  they  furnish 
only  in  small  amounts.  For  its  building  purposes  the 
body  picks  out  from  the  blood  as  much  of  each  of  the 
different  amino-acids  as  it  needs,  using  the  remainder 
for  fuel  as  it  uses  sugar  and  fats. 

Meat,  fish,  milk,  and  egg  proteins  are  complete ;  they 
supply  in  large  amounts  all  the  amino-acids  that  the 
body  needs.  The  proteins  of  grains,  beans,  and  peas  are 
low  in  certain  amino-acids  and  must  be  eaten  in  large 


FIGS.  122  and  123.  A  Roman  and  a  Japanese 
soldier.  They  made  their  reputations  as 
fighters  on  a  low-protein  diet. 


1 68  PRIMER   OF  PHYSIOLOGY 

amounts  if  they  are  the  sole  source  of  protein  supply. 
Potato  protein  seems  to  be  of  good  quality,  although  it 
is  supplied  in  only  small  amounts.  When  a  number  of 
different  kinds  of  foods  are  eaten,  the  amino-acids  lack- 
ing in  one  food  may  be  furnished  by  another,  and  thus 
all  the  needs  of  the  body  will  be  met.  All  the  protein 
needs  of  the  body  can  be  met  with  vegetables,  but  in- 
cluding meat,  milk,  or  eggs  makes  it  much  easier  to  plan 
a  satisfactory  diet.  The  proteins  of  soy  beans  and  of 
peanuts  are  of  better  quality  than  most  vegetable  pro- 
teins. Gelatin  is  a  protein  of  very  low  grade. 

The  muscular  endurance  of  low-protein  subjects.  All 
vegetarians  live  on  a  low  protein  diet.  That  it  is  pos- 
sible to  maintain  the  body  in  health  and  strength  on 
such  a  diet  is  shown  by  the  muscular  endurance  of  vege- 
tarians. In  one  seven-day  walking  race  of  372  miles, 
two  vegetarians  won  first  and  second  places,  beating 
the  fastest  flesh  eater  by  22  hours.  In  another  great 
walking  race  of  124^  miles,  in  which  there  were 
thirty-two  competitors,  the  first  six  men  who  arrived 
were  vegetarians,  the  seventh  and  eighth  were  meat 
eaters,  and  the  ninth,  tenth,  eleventh,  and  twelfth 
were  vegetarians.  In  January,  1912,  the  Edinburgh 
Marathon  race  (25  miles)  was  won  by  the  Finnish 
runner,  Kolehmainen,  who  is  a  vegetarian.  This  same 
man  in  the  1912  Olympic  games  at  Stockholm  went 
to  the  post  on  six  successive  days  against  the  best 
runners  of  all  the  world,  and  six  times  he  defeated 
them  all  so  easily  that  he  is  declared  to  be  "  the  greatest 
of  all  Olympic  heroes  —  the  best  long  distance  runner 
who  ever  wore  spiked  shoes." 

Many  other  athletic  contests  have  been  won,  and  are 


FOODS  AND   HEALTH 


169 


IO 

minutes 


FIG.  124.    The  low-pro- 


being  won,  by  vegetarians,  but  since  in  all  cases  of  this 
kind  much  depends  upon  the  individual,  we  shall  give 
some  average  endurance  tests  that 
have  been  tried  on  a  number  of  in- 
dividuals at  the  same  time.  Professor 
Irving  Fisher  of  Yale  University  se- 
lected fifteen  athletes  who  were  living 
on  a  high-protein  diet  and  tested  their 
endurance.  He  found  that  on  the 
average  they  were  able  to  hold  their 
arms  extended  for  ten  minutes.  One 
man,  who  was  a  baseball  pitcher  and 
had  powerful  shoulder  muscles,  was 
able  to  hold  his  arm  extended  for  22 
minutes.  The  endurance  of  thirty- 
two  young  men,  vegetarians  and  low-  tein  subjects  held  their 

.    .  i  .  i  .,  -,    ^  arms  extended   for   49 

protein  subjects,  but  not  athletes,  was  minutes  on  an  average . 
then  tested  by  the  same  method,  the  high-protein  subjects 
These  men  were  able  to  keep  their  forl° minutes' 
arms  extended  on  an  average  for  49  minutes,  practically 
five  times  as  long  as  their  meat-eating  competitors.  One 
of  them  made  a  record  of  200  minutes,  more  than  nine 
times  as  long  as  the  best  high-protein  athlete. 

Nine  of  the  Yale  athletes  were  then  given  the  deep 
knee-bending  test.  On  an  average  they  were  able  to 
go  through  with  this  exercise  383  times.  Twenty-one 
low-protein  subjects  were  given  the  same  test  and  their 
average  record  was  833  times.  At  a  later  time  one  of 
the  low-protein  subjects,  a  young  man  twenty-two  years 
old,  who  had  lived  on  a  vegetable  diet  for  two  years, 
made  the  deep  knee-bend  5002  times,  1555  times  more 
than  it  was  made  by  all  the  nine  high-protein  athletes. 


1 70  PRIMER    OF  PHYSIOLOGY 

Objections  to  a  heavy  meat  diet.  Because  meat  is  rich 
in  protein,  much  of  the  discussion  as  to  the  protein  needs 
of  the  body  has  centered  about  the  advisability  of  eating 
meat.  Some  persons  have  insisted  that  it  is  injurious 
to  the  body  and  that  it  should  not  be  used  at  all  as  an 
article  of  food.  As  we  have  shown,  it  is  possible  to 
keep  the  body  in  health  with  a  vegetable  diet,  provided 
milk  is  also  used,  but  there  is  no  proof  that  a  moderate 
amount  of  meat  is  harmful  to  the  average  person.  But 
because  meats  are  pleasant  to  the  taste,  very  large 
amounts  of  them  are  sometimes  eaten.  This  is  objec- 
tionable for  the  following  reasons  : 

1 i)  Meat  does  not  supply  the  minerals  and  the  vitamins 
that  the  body  needs.     If  large  amounts  of  meat  are  eaten, 
small  quantities  of  other  foods  will  be  taken  and  some 
of.  the  needs  of  the  body  may  not  be  supplied. 

(2)  Large  amounts  of  meat  in  tJie  diet  cause  poisonous 
substances  to  be  formed  in  tJie  intestine)-     When  more 
protein  is  eaten  than  the  pepsin  and  trypsin  can  digest 
in  a  reasonable  time,  part  of  it  passes  undigested  into 
the  large  intestine.     Here  bacteria  cause  it  to  decay,  and 
in  the  process  of  decay  poisonous  substances  are  formed. 
These  poisons  are  then  absorbed  into  the  body,  and  they 
cause  headaches  and  other  disturbances  by  poisoning 
the  cells. 

(3)  Meat  does  not  supply  the  bulk  that  is  needed  in  the 

1  Individuals  differ  enormously  in  the  kinds  of  bacteria  that  grow  in  the 
intestines  and  in  the  amount  of  poison  formed  by  them,  and  these  sub- 
stances are  often  abundant  in  the  intestines  of  animals  that  live  on  a 
vegetable  diet  as  well  as  in  the  intestines  of  meat -eating  animals.  Never- 
theless, it  is  true  that  in  the  average  person  a  diet  of  vegetables  and  milk 
causes  small  quantities  of  the  poisons  to  be  formed,  and  a  diet  of  meat  and 
eggs  causes  an  increased  quantity  of  them  to  be  formed. 


FOODS  AND  HEALTH  I/I 

diet.  The  lack  of  bulky  material  causes  the  wastes  to 
lie  for  a  long  time  in  the  intestine,  and  this  causes  more 
of  the  poisons  to  be  absorbed  from  these  wastes  than 
would  be  absorbed  if  they  were  promptly  removed  from 
the  body. 

(4)  A  heavy  meat  diet  loads  tJie  system  with  protein 
wastes.  This  is  probably  injurious,  in  some  cases  at 
least.  It  has  long  been  believed  by  many  physicians 
that  an  excess  of  substances  of  the  uric  acid  class  is  the 
cause  of  gout  and  other  serious  ailments.  Part  of  the 
trouble,  at  least,  seems  to  lie  somewhere  in  the  protein 
wastes,  and  the  patients  are  benefited  by  cutting  the 
protein  to  a  low  point. 

Because  of  these  facts  it  is  wise  to  eat  only  moder- 
ately of  meats  and  to  use  other  articles  of  food  more 
liberally  than  they  are  used  when  meat  is  taken  in  large 
amounts. 

The  energy  needs  of  the  body.  The  body  must  have 
enough  food  to  provide  it  with  heat  and  with  strengtJi  for 
the  work  tJiat  it  does.  A  certain  amount  of  food  is 
burned  in  the  body,  even  when  the  body  is  completely 
at  rest.  After  eating,  the  amount  of  food  burned  by 
the  cells  is  greater.  When  work  is  done  by  the  muscles, 
the  amount  of  food  used  is  increased, — enormously  in- 
creased if  hard  work  is  done.1  Exposure  to  cold  causes 
the  muscles  to  have  a  greater  tension,  and  thus  increases 
the  amount  of  food  burned  in  the  body  and  the  amount 

1  The  energy  content  of  food  is  measured  by  the  heat  it  yields  when 
burned.  The  unit  of  measurement  is  the  calorie,  which  is  the  amount  of 
heat  required  to  raise  a  liter  of  water  one  degree  Centigrade.  Roughly,  it 
is  the  amount  of  heat  required  to  raise  one  quart  of  water  two  degrees 
Fahrenheit.  The  body  gets  the  equivalent  of  about  4  calories  of  heat  for 
each  gram  of  dry  carbohydrate  or  protein  eaten,  and  about  9  calories  from 


1/2  PRIMER   OF  PHYSIOLOGY 

of  heat  released.  Cold  also  causes  a  person  to  move 
about  more,  and  to  swing  the  arms  and  stamp  the  feet, 
which  increases  the  heat  production  of  the  body  ;  it  may 
cause  shivering,  which  brings  still  other  muscles  into 
use.  In  young  persons  the  food  is  burned  very  rapidly 
in  the  cells,  a  boy  or  girl  of  ten  or  twelve  years  requiring 
as  much  food  as  a  man  or  woman,  and  young  persons  of 
16  and  17  years  much  more  than  middle-aged  persons. 
Women  require  somewhat  less  food  than  men,  and  in 
old  persons  the  food  is  not  used  so  rapidly  by  the 
cells. 

Effects  of  a  diet  that  does  not  yield  enough  energy.  A 
group  of  young  men  placed  on  a  diet  that  yielded  in- 
sufficient energy  continued  to  grow  thinner  until  they 
had  lost  a  little  more  than  10  per  cent  of  their  weight. 
After  that  their  bodies  burned  less  food,  and  they  con- 
tinued to  live  on  this  low  level  without  further  loss  of 
weight.  They  did  not  become  ill,  but  they  lacked  vigor, 
and  when  they  attempted  severe  muscular  exercise  they 
found  that  they  lacked  strength  for  it. 

During  the  recent  war  many  millions  of  persons  were 

each  gram  of  fat.  An  average-sized  man  needs  enough  food  to  yield  the 
following  numbers  of  calories : 

Absolute  rest  in  bed  without  food 1680  calories 

Absolute  rest  in  bed  with  food 1840  calories 

Office  work  or  other  light  work,  about 2500  calories 

Light  muscular  work 2700  calories 

Moderately  active  muscular  work,  as  work  of  farmer  or 

mechanic      » 34°°  calories 

Hard  muscular  work 4000  calories 

Very  hard  muscular  work 6000  calories 

In  a  boys'  school  where  most  of  the  pupils  were  from  13^  to  16  years 
of  age,  the  food  used  had  a  value  of  almost  5000  calories  for  each  pupil. 


FOODS  AND  HEALTH  173 

forced  to  live  on  this  low  plane,  and  at  all  times  great 
numbers  of  persons  in  all  countries  are  undernourished. 
This  is  especially  true  of  children ;  among  both  the  rich 
and  the  poor  great  numbers  of  boys  and  girls  are  under- 
fed. Sometimes  this  is  because  not  enough  food  is 
provided.  More  often  it  is  because  the  child  is  not 
hungry  and  eats  only  certain  of  the  articles  of  food  that 
are  placed  on  the  table.1  Such  children  are  in  a  low 
state  of  vigor,  they  do  not  grow  fast  enough,  and  it  is 
believed  that  they  have  less  resistance  to  infections  than 
they  would  have  if  they  were  well  nourished.  The  best 
indication  as  to  whether  enough  food  is  being  provided 
is  the  weight. 

Food  for  energy.  Bread,  grains,  potatoes,  butter,  sugar, 
and  fat  meats  are  the  foods  on  which  we  mainly  depend 
for  our  energy.  The  body  can  use  for  fuel  purposes  any 
protein  that  is  not  needed  for  building  material ;  but 
proteins  are  expensive  foods,  and,  as  we  have  seen  above, 
it  is  not  wise  to  eat  too  heavily  of  them.  The  thing 
to  do,  therefore,  is  to  eat  the  proteins  that  we  need  for 
building  material  and  then  take  enough  fats,  starches, 
and  sugars  to  give  us  plenty  of  heat  and  strength.  Usu- 
ally we  can  trust  our  appetites  to  tell  us  when  we  have 
had  enough  of  these  foods.  Taking  food  into  the  body 
increases  the  amount  that  is  burned  in  the  cells,  and  the 
amount  of  body  heat  produced.  Carbohydrates  in- 
crease the  heat  production  least,  fats  increase  it  more, 

1  The  sensation  of  hunger  is  due  to  the  contraction  of  the  muscles  of 
the  stomach,  and  these  muscles  do  not  necessarily  contract  when  the  body 
needs  food.  It  is  generally  supposed  that  children  overeat,  but  far  more 
of  them  do  not  eat  enough.  The  trouble  comes  from  the  fact  that  they  eat 
too  much  of  sweets  or  other  foods  that  gratify  the  appetite  and  refuse 
many  articles  of  ordinary  food. 


174  PRIMER   OF  PHYSIOLOGY 

and  proteins  increase  it  most  of  all.  A  winter  diet, 
therefore,  should  be  higher  in  fats  and  protein  than  a 
summer  diet.  Meat  helps  to  keep  up  the  body  heat  in 
winter,  and  a  diet  consisting  largely  of  fruits  and  vege- 
tables is  advisable  on  hot  summer  days. 

The  mineral  supply  of  the  body.  This  subject  has 
already  been  discussed  (Chapter  16).  In  general,  eat- 
ing large  amounts  of  meat  and  sugar  causes  a  lack  of 
minerals,  and  a  diet  of  vegetables  and  milk  supplies 
minerals.  Of  all  the  minerals,  the  one  most  commonly 
lacking  is  calcium,  which  can  be  supplied  by  the  free  use 
of  leaf  vegetables  and  milk. 

The  vitamin  supply.  Whole  grains,  peas,  beans,  and 
vegetables  contain  abundant  supplies  of  the  vitamin  that 
prevents  beriberi.  Milk  is  moderately  rich  in  this  sub- 
stance. Practically  all  of  our  population  have  enough 
of  this  material.  The  other  vitamin  is  found  in  the 
leaves  of  plants,  in  the  yolk  of  eggs,  and  in  milk  and 
butter.  An  animal  like  the  cow  or  rabbit  can  eat  enough 
grass  or  leaves  to  supply  it  with  this  vitamin,  but  a 
human  being  cannot  do  this.  Milk  and  butter  should 
therefore  be  used.  The  livers  and  kidneys  of  animals 
supply  this  second  vitamin  (it  is  found  in  cod-liver  oil), 
and  it  is  reported  to  be  present  in  the  fat  of  fish. 

General  dietary  principles.  The  seeds  of  plants  are 
our  chief  source  of  food ;  wheat  and  corn  bread,  break- 
fast foods,  oatmeal,  rice,  macaroni,  peas,  beans,  and 
nuts  make  up  the  greater  part  of  the  diet  of  the  people 
in  temperate  climates.  Fruits  and  vegetables  like  pota- 
toes, turnips,  and  carrots  furnish  about  the  same  elements 
to  the  body  as  grains.  A  diet  composed  of  these  foods 
is  likely  to  lack  certain  of  the  needed  amino-acids, 


FOODS  AND  HEALTH  175 

calcium,  and  the  vitamin  found  in  leaf  vegetables,  eggs, 
and  milk.  Meat  will  make  good  the  lack  in  the  protein, 
but  it  will  not  supply  the  calcium  or  the  vitamin,  and  to 
make  the  diet  complete  eggs  or  milk,  or  leaf  vegetables, 
must  be  used.  As  we  have  already  seen,  it  is  difficult 
for  man  to  eat  enough  green  vegetables  to  supply  the 
lacking  substances,  and  for  this  reason  eggs  and  milk, 
especially  milk,  should  be  used.  Grains,  vegetables  like 
the  potato,  fruits,  and  meat  do  not  make  a  complete  diet. 
Leaf  vegetables,  milk,  or  eggs  also  are  necessary. 

The  importance  of  milk  in  the  diet.  All  who  under- 
stand the  food  needs  of  the  body  are  agreed  that  it  is  a 
great  misfortune  that  many  families  are  using  less  milk 
than  formerly  because  of  an  increase  in  its  price.  Milk  is 
still  one  of  the  cheapest  of  our  foods ;  a  quart  of  it  con- 
tains almost  as  much  energy  as  a  pound  of  steak,  and  it 
contains  minerals  and  vitamins  that  can  be  supplied  in 
an  ordinary  diet  by  nothing  else.  A  certain  organiza- 
tion that  has  long  been  at  work  to  improve  the  diets  of 
poor  persons  says  that  a  quart  of  milk  should  be  provided 
each  day  for  a  child  and  a  pint  for  an  adult.  A  noted 
authority  on  foods  has  stated  that  good  ffiilk  is  worth 
whatever  it  costs  to  produce  it,  and  that  no  meat  should 
be  bought  until  each  member  of  the  family  has  been 
provided  with  a  pint  of  milk.  Another  authority  on 
foods  reports  that  in  his  own  family  from  25  to  30  per 
cent  of  all  the  money  expended  for  food  is  used  in  the 
purchase  of  milk.  The  most  serious  mistake  made  by 
our  people  in  the  purchase  of  food  is  in  not  buying 
enough  milk.  In  the  southern  part  of  the  United  States 
it  is  especially  important  that  the  people  in  small  villages 
and  in  the  country  provide  a  supply  for  themselves. 


176  PRIMER    OF  PHYSIOLOGY 

Large  quantities  of  sugar  injurious  to  the  digestive 
organs.  In  his  wild  state  man  secured  most  of  his  sugar 
by  eating  starchy  foods  and  digesting  them  to  malt 
sugar.  Now  he  prepares  great  quantities  of  sugar  and 
uses  it  in  his  food,  but  the  sugar  that  comes  from  cane 
and  beets  is  cane  sugar  and  not  malt  sugar.  This  sugar, 
when  taken  in  large  quantities,  is  very  irritating  to  the 
stomach,  and  because  in  large  amounts  it  is  not  a  natural 
food  for  man  we  have  but  a  small  quantity  of  the 
enzyme  that  digests  it.  When  a  large  amount  of  sugar 
is  eaten,  therefore,  it  may  remain  for  a  long  time  undi- 
gested in  the  small  intestine,  and  when  this  occurs  the 
sugar  is  likely  to  be  fermented  by  bacteria  and  injurious 
acids  formed  from  it.  Sugar  should  be  taken  in  moder- 
ate quantities,  and  it  should  be  mixed  with  other  foods 
and  not  eaten  at  a  time  when  it  will  form  a  thick,  sirupy 
solution  in  an  otherwise  empty  stomach.  A  moderate 
quantity  of  candy  eaten  at  the  close  of  a  meal  has  a  very 
different  effect  on  the  digestive  system  from  that  of  a 
large  quantity  taken  before  a  meal. 

Fats.  Fats  hinder  stomach  digestion,  and  except  in 
very  cold  wdather  few  persons  can  take  a  daily  ration 
of  more  than  three  and  a  half  ounces  of  fat  without  bad 
results.  Persons  who  suffer  from  acid  stomach  are  ad- 
vised to  eat  liberally  of  fatty  foods,  and  about  two  ounces 
of  fat  should  be  included  in  the  average  daily  diet. 
Certain  individuals  who  refuse  to  eat  butter,  fat  meat, 
olive  oil,  or  other  fatty  foods,  live  on  very  small  quanti- 
ties of  fat,  and  get  their  energy  almost  entirely  from 
carbohydrates.  This  leaves  the  lipase  without  any  work 
to  do  and  throws  a  heavy  task  on  the  starch-digesting 
enzymes,  and  it  is  not  so  likely  to  give  a  well-ordered 


FOODS  AND  HEALTH  177 

digestion  as  a  mixed  diet.  It  is  also  believed  that  the 
cells  of  the  body  keep  in  better  health  when  part  of  their 
nourishment  is  supplied  in  the  form  of  fat ;  that  persons 
who  eat  little  fat  are  more  subject  to  germ  diseases, 
especially  tuberculosis,  than  are  those  who  eat  reason- 
able quantities  of  fatty  foods.1  During  the  war  more 
hardship  seems  to  have  been  caused  by  a  lack  of  fats 
than  by  a  shortage  of  any  other  class  of  foods. 

Eating  vegetables  beneficial  to  the  health.  Coarse 
vegetable  foods  like  string  beans,  cabbage,  cauliflower, 
carrots,  turnips,  potatoes,  beets,  radishes,  asparagus,  let- 
tuce, celery,  and  spinach  are  very  necessary  to  the  health. 
They  furnish  minerals  to  the  body  and  after  they  are 
digested  there  remains  much  bulky  refuse  matter  that 
causes  the  wastes  to  be  moved  rapidly  along  the  intes- 
tine. These  are  the  foods  that  are  least  palatable  to 
most  persons,  and  they  are  the  ones  that  are  most  fre- 
quently left  out  of  the  diet.  One  difficulty  in  getting 
enough  of  these  vegetables  into  the  diet  is  that  in  the 
country  the  family  garden  is  often  neglected  and  a  suffi- 
cient variety  of  them  is  not  produced.  Another  difficulty 
is  that  in  towns  and  cities  these  vegetables  are  often 
needlessly  allowed  to  wilt  in  stores  and  markets,  and 
their  tenderness  is  lost  before  they  are  cooked.  The 
chief  difficulty,  however,  is  that  only  a  few  persons  un- 

1  Fat  is  considered  the  most  important  part  of  the  diet  in  tuberculosis. 
Outdoor  life  in  this  disease  is  more  beneficial  in  cold  climates  than  in  warm 
climates  and  more  beneficial  in  winter  than  in  summer.  Some  physicians 
think  that  this  is  because  in  winter  the  exposure  to  the  cold  increases  the 
appetite  for  fat.  Milk  and  eggs  have  always  been  used  as  a  source  of 
much  of  the  fat  in  the  treatment  of  tuberculosis,  and  it  is  possible  that  a 
part  of  the  benefits  that  are  supposed  to  come  from  the  fats  in  the  diet  is 
due  to  an  abundant  supply  of  the  vitamin  that  is  found  in  these  foods. 


1/8  PRIMER   OF  PHYSIOLOGY 

derstand  how  to  cook  vegetables  so  that  they  will  come 
to  the  table  with  the  attractive  flavors  and  odors  that  an 
expert  vegetable  cook  can  bring  out.  Because  it  is  a 
difficult  art  to  do  this,  many  housewives  give  their  atten- 
tion to  the  easier  and  simpler  tasks  of  cooking  meats  and 
of  making  pies,  cakes,  and  desserts,  and  serve  on  their 
tables  vegetables  cooked  in  an  unappetizing  way.  It  is 
very,  important  that  the  proper  attention  be  given  to  the 
raising  and  preparation  of  these  foods,  and  every  young 
person  should  learn  to  eat  all  the  different  kinds  of 
vegetables  that  are  served  in  his  home. 

A  plan  for  getting  a  proper  diet.  Since  the  very  life 
of  the  body  centers  around  the  food  from  which  the  cells 
build  their  living  substances  and  from  which  they  get 
their  energy,  it  is  easy  to  understand  that  the  question  of 
diet  is  the  most  important  problem  of  all  hygiene.  It  is 
not  possible  to  give  any  simple  rules  that  will  always  be 
a  complete  guide  in  eating,  but  the  following  suggestions 
may  be  helpful: 

(1)  Eat  enough  food.     Only  the  energy  needs  of  the 
body  are  increased  by  work,  and  laborers  who  eat  large 
quantities  of  food  are  not  nearly  so  likely  to  suffer  from 
a  lack  of  protein,  minerals,  and  vitamins  as  those  who 
take  little  exercise  and  eat  only  small  amounts  of  food. 
Enough  should  be  eaten  to  keep  up  the  weight  and  vigor 
of  the  body. 

(2)  Eat  many  different  kinds  of  foods.     As  far  as  it  is 
possible  to  do  so,  make  it  a  rule  to  eat  at  each  meal  one 
food  rich  in  protein,  like  lean   meat,  eggs,  beans,   or 
cheese ;  one  or  more  starchy  foods  like  breakfast  foods, 
bread,  macaroni,  or  potatoes  ;  some  fatty  food  like  butter, 
fat  meat,  or  nuts ;  some  coarse  vegetable  food  like  cab- 


FOODS  AND   HEALTH 


179 


bage,  asparagus,  turnips^  or  beets ;  a  moderate  amount 
of  some  sweet  food  like  sugar,  sirup,  preserves,  jelly, 
honey,  cake,  or  a  sweet  dessert.  Follow  this  plan,  and  you 
will  probably  not  be  tempted  to  eat  too  heavily  of  any  one 


FIGS.  125,  126,  and  127.     Healthful  sports  and  games   do   much  to  prevent 
constipation. 

kind  of  food  and  will  supply  your  body  with  all  the  dif- 
ferent materials  that  it  needs. 

(3)  Include  milk  and  butter  in  the  diet.  If  this  third 
rule  is  followed  in  connection  with  the  two  rules  pre- 
viously given,  the  food  needs  of  the  body  will  be  met. 

It  is  very  important  to  follow  some  plan  that  will 
cause  enough  food  to  be  eaten  and  all  the  different  ma- 
terials that  are  needed  to  be  supplied ;  for  experience 
has  proved  that  persons  who  simply  follow  their  appe- 
tites or  eat  the  foods  that  can  be  most  conveniently 
secured  frequently  fail  to  supply  their  bodies  with  some 
of  the  materials  that  they  need. 

Constipation  a  deadly  enemy  to  health.  No  matter 
what  diet  is  eaten,  unless  the  wastes  are  rapidly  moved 
along  the  intestine  and  promptly  cleared  out  of  the 
body,  ill-smelling  gases  and  poisons  will  be  formed  in 
the  refuse  matter  in  the  large  intestine.  These  will  be 
absorbed  into  the  bloocl  and  cause  bad  breath,  headaches, 


ISO  PRIMER   OF  PHYSIOLOGY 

and  other  evil  consequences.  In  selecting  a  diet,  enough 
coarse  food  should  be  chosen  to  give  large  amounts  of 
bulky  refuse  matter.  This  will  assist  in  causing  the 
wastes  to  be  moved  rapidly  along  the  intestine. 

Other  important  points  in  the  prevention  and  cure  of 
constipation  are  vigorous  exercise,  especially  bendings 
of  the  body  and  movements  of  the  legs  that  will  press 
the  digestive  organs  about  and  help  the  circulation  of 
the  blood  through  them ;  massage  of  the  abdomen, 
which  also  helps  the  circulation  of  the  blood  through  the 
stomach,  liver,  and  intestines ;  a  daily  cool  or  cold  bath  ; 
attending  to  emptying  the  bowels  regularly  at  a  certain 
hour  each  day1;  eating  foods  like  fruits,  corn  meal,  and 
graham  flour,  which  have  a  natural  laxative  effect;  drink- 
ing large  quantities  of  water,  especially  at  bedtime ;  and 
keeping  the  nervous  system  in  good  condition  so  that  the 
digestive  organs  will  be  properly  regulated.  A  few 
physicians  now  understand  how  to  treat  successfully  pa- 
tients suffering  from  constipation,  and  any  one  who  suf- 
fers ill  health  month  after  month  because  of  poisons 
produced  in  his  own  body  should,  if  possible,  put  himself 
in  charge  of  a  physician  who  is  especially  qualified  to 
treat  this  trouble. 

The  cost  of  food.  The  object  of  eating  is  to  supply 
the  body  with  building  material,  heat,  and  strength.  To 

1  An  X-ray  examination  of  animals  shows  that  before  the  bowels  are 
emptied  the  part  of  the  large  intestine  which  runs  across  the  body  is 
raised  up  partially  on  end  and  the  part  which  runs  up  the  right  side  of  the 
body  is  dragged  across  to  take  the  place  of  the  transverse  portion.  It  takes 
about  20  minutes  for  these  changes  in  the  position  of  the  large  intestine  to 
be  brought  about.  It  is  possible  to  train  the  nerves  that  control  the  intes- 
tine until  they  will  set  the  muscles  of  the  intestine  in  action  at  regular 
times,  and  it  is  exceedingly  important  to  do  this. 


FOODS    AND   HEALTH  l8l 

make  sure  that  all  the  needs  of  the  body  are  supplied,  we 
must  eat  foods  of  different  kinds ;  we  cannot  live  on 
corn  meal  and  beans,  no  matter  how  cheap  they  may  be. 
It  is  often  possible,  however,  to  supply  the  needs  of  the 
body  either  with  high-priced  foods  or  with  other  foods 
that  may  be  purchased  at  a  much  lower  rate.  For  ex- 
ample, the  same  amount  of  energy  that  can  be  purchased 
in  wheat  flour  for  four  cents  costs  ninety-five  cents  in 
oysters,  and  protein  costs  nine  times  as  much  in  canned 
corn  as  in  corn  meal. 

The  average  family  is  not  wealthy,  and  according  to 
the  best  statistics  available  it  is  slightly  undernourished. 
We  cannot  go  into  the  question  of  food  costs  further 
than  to  point  out  that  in  our  country  millions  of  dollars 
might  be  saved  each  year  and  the  health  of  millions  of 
people  greatly  improved,  if  the  persons  purchasing  the 
food  supplies  of  families  understood  how  to  secure  the 
most  nourishment  for  the  money  that  they  have  to  ex- 
pend. The  average  American  family  spends  about  one 
third  of  the  money  used  for  the  purchase  of  foods  for 
meats,  fish,  and  poultry  and  less  than  one  tenth  of  it  for 
milk.  Undoubtedly  the  diet  would  be  improved  by 
spending  more  for  milk  and  less  for  meat. 

QUESTIONS 

How  much  protein  is  eaten  daily  by  the  average  prosper- 
ous American  or  European  ?  Into  what  are  the  proteins  split 
in  digestion  ?  For  what  special  purpose  are  ammo-acids 
used  by  the  cells  ?  How  do  proteins  differ  as  to  the  amino- 
acids  they  supply?  Name  some  foods  that  furnish  protein  of 
high  grade ;  some  foods  that  furnish  less  valuable  protein. 
Give  some  arguments  for  a  low-protein  diet  based  on  the 


1 82  PRIMER   OF  PHYSIOLOGY 

muscular  endurance  of  vegetarians  and  other  low-protein  sub- 
jects. Give  four  objections  to  a  heavy  meat  diet. 

How  much  food  does  the  body  need?  At  what  time  of 
life  is  most  food  required  ?  What  is  the  result  of  living  on  a 
diet  that  does  not  supply  enough  energy?  What  shows 
whether  enough  food  is  being  provided  ?  Is  your  weight 
what  it  ought  to  be  ? 

What  foods  furnish  an  abundance  of  minerals  to  the 
body?  What  foods  are  rich  in  each  of  the  vitamins  ? 

Name  some  of  the  chief  energy-yielding  foods.  What  class 
of  foods  most  increases  the  heat  production  of  the  body  ?  What 
foods  can  be  used  to  increase  the  heat  production  of  the  body 
in  winter  ?  What  foods  will  keep  the  amount  of  body  heat 
produced  lowest  in  hot  weather  ? 

What  other  classes  of  foods  supply  the  same  materials  as 
seeds  ?  What  needed  substances  are  lacking  in  these  foods  ? 
Explain  how  each  of  these  substances  may  be  supplied. 
Why  is  it  important  that  milk  be  used  freely? 

Why  is  sugar  injurious  to  the  stomach  and  intestines  when 
eaten  in  large  quantities  ?  When  is  the  proper  time  to  eat 
candy  ?  How  much  fat  should  be  included  in  the  daily  ration? 
Why  is  it  unwise  to  depend  entirely  upon  carbohydrate  foods 
for  energy  and  to  exclude  fatty  foods  from  the  diet? 

Why  are  coarse  vegetable  foods  necessary  for  the  health  ? 
Give  some  of  the  reasons  why  these  foods  are  often  omitted 
from  the  diet. 

Give  three  rules  for  eating  that  will  help  in  giving  the  body 
a  proper  food  supply.  Why  is  it  important  that  some  plan  be 
followed  in  supplying  the  body  with  food  ? 

Why  is  it  necessary  for  the  wastes  to  be  promptly  removed 
from  the  intestines  ?  How  do  coarse,  bulky  foods  assist  in 
this  ?  Give  some  important  points  in  the  prevention  and  cure 
of  constipation.  How  does  a  knowledge  of  foods  help  in  se- 
curing a  satisfactory  diet  at  a  moderate  cost  ? 


.CHAPTER   NINETEEN 

THE   TEETH 

THE  teeth  are  composed  of  the  hardest  tissues  in  the 
body,  but  decay  of  the  teeth  is  the  most  common  bacte- 
rial disease  of  man.  Unlike  many  other  infections,  this 
disease  runs  on  and  on,  and  can  be  checked  only  by 
a  surgical  operation  that  removes  the  infected  tissues 
and  the  germs  that  are  in  them.  We  have  therefore  a 
whole  class  of  surgeons  (dental  surgeons)  who  give  their 
entire  time  to  the  treatment  and  prevention  of  infections 
of  the  teeth  and  their  surrounding  parts.  In  recent 
years  it  has  been  proved  that  defective  teeth  are  more 
injurious  to  the  health  than  had  been  suspected,  and  the 
importance  of  keeping  the  teeth  sound  can  hardly  be 
exaggerated. 

How  bad  teeth  injure  the  health.  Bad  teeth  cause  the 
food  to  be  swallowed  in  large  pieces  and  thus  greatly 
delay  digestion.  They  also  allow  germs  to  gain  entrance 
to  the  bones  of  the  jaw  and  establish  centers  of  infection 
in  these  parts.  These  germs  are  usually  slow-growing 
races  of  streptococci  that  live  in  the  bones  for  years,  and 
often  the  health  is  greatly  injured  by  the  toxins  that  are 
absorbed  from  them.  Frequently  the  germs  are  carried 
from  the  teeth  to  other  parts  of  the  body  and  by  grow- 
ing in  these  parts  cause  rheumatism,  heart  disease,  kid- 
ney disease,  and  other  ailments.  This  subject  will  be 
discussed  in  a  later  chapter  (pages  233  and  242). 

The  structure  of  a  tooth.  A  tooth  is  composed  of  a 
crown,  a  neck,  and  one  or  more  roots.  The  main  bulk  of 
the  tooth  is  composed  of  dentine,  or  ivory,  a  substance 
harder  than  the  most  compact  bone.  The  crown  is  cov- 
ered by  a  coat  of  enamel.  This  substance  is  very  hard, 

183 


1 84 


PRIMER   OF  PHYSIOLOGY 


enamel 


dentine 


bone 


but  brittle  like  glass.  The  enamel  can  easily  be  broken 
by  biting  on  hard  objects,  and  it  may  be  cracked  by  very 
hot  food  or  drink  taken  into  the  mouth.  If  it  is  once 
broken  off  it  is  never  replaced,  and  without  the  covering 

of  enamel  over  it  the  den- 
tine soon  decays.  The 
roots  of  the  teeth  stand  in 
sockets  in  the  jaw-bones 
and  are  covered  by  a 
layer  of  bone-like  cement. 
Lining  the  socket  in  which 
the  root  stands  is  a  layer 
of  connective  tissue  that 
fastens  together  the  root 
and  the  bone  of  the  jaw. 
In  the  center  of  the 

tooth  is  the  pulp  cavity,  a 
bundle  of  nerves, 

veins,  and  arter-   little  chamber  containing 
iesfor  pulp         nerves  and  blood  vessels. 

FIG.  128.   A  section  through  a  tooth    Break  open,  the  tooth  of 

showing  its  structure  and  how  it  is  fas-  an  animal  and  you  will 
tened  into  the  jaw-bone. 

easily    find    the    enamel, 

the  dentine,  the  pulp  cavity,  and  the  little  root  canals 
through  which  the  nerves  and  blood  vessels  enter  from 
the  jaw-bone. 

Why  a  tooth  decays.  Decay  of  the  teeth  is  caused  by 
bacteria  that  grow  in  the  materials  that  stick  to  the 
teeth  and  lodge  between  them.  It  is  thought  that  the 
bacteria  start  the  decay  by  forming  acids  that  eat  away 
the  enamel.  Then  other  kinds  of  bacteria  enter  the 
cavity  and  destroy  the  dentine.  If  the  decay  is  allowed 
to  go  on  until  the  pulp  is  reached,  this  is  killed  and  the 


THE  TEETH  1 85 

germs  not  only  grow  in  the  dead  pulp  but  enter  the  jaw- 
bone through  the  root  canal  and  set  up  their  growth 
about  the  end  of  the  root.  When  the  decay  is  reaching 
the  pulp,  but  when  the  nerve  endings  in  the  pulp  are 
not  yet  dead,  the  tooth  may  ache.  A  gum  boil  is  due  to 
infection  at  the  root  of  a  tooth. 

The  teeth  preserved  by  keeping  them  clean.  The  way 
to  preserve  the  teeth  is  to  keep  them  clean,  so  that 
bacteria  cannot  find  a  home  around  them.  The  teeth 
should  be  brushed  both  inside  and  outside  after  each 
meal,  and  food  that  is  lodged  between  them  should  be 
carefully  removed.  This  point  is  important  because 
decay  nearly  always  begins  between  the  teeth.  Some 
dentists  recommend  that  the  food  be  removed  with  den- 
tal floss,  but  in  the  hands  of  the  average  person  a  tooth- 
pick is  more  effective.  A  quill  pick  is  less  likely  to 
injure  the  gums  than  a  wooden  or  metal  one.  Rinsing 
water  about  vigorously  in  the  mouth  and  driving  it  be- 
tween the  teeth  removes  many  small  food  particles,  and 
this  should  always  be  done  after  the  teeth  have  been 
brushed. 

A  good  tooth  powder  or  paste  is  an  aid  in  cleaning 
the  teeth.  Prepared  powders  or  pastes  may  be  used, 
or  a  good  powder  made  of  precipitated  chalk  and 
powdered  orris  root, 
which  may  be  pur- 
chased from  any  drug- 
gist. Charcoal,  pumice 
stone,  or  other  gritty 
substances  should  not 

,  ,  ,  ,      FIG.  129.    A   curved  brush  with  the  bristles 

be  used,  as  they  scratch  longer  at  the  ends  cleans  ^  teeth  lieMKr  than 
the  teeth  and  leave  a  straight  brush. 


1 86 


PRIMER   OF  PHYSIOLOGY 


little  grooves  in   the   surface  where  food  and  bacteria 
collect.     A  curved  brush  with  the  bristles  longer  at  the 


FlG.  130.     One  half  of  the  permanent  set  of  teeth. 

ends  cleans  the  teeth  better  than  a  straight  brush  ;  a 
medium-sized  brush  with  moderately  stiff  bristles  should 
be  used. 

Deposits  on  the  teeth.  The  mucus  of  the  saliva  forms 
a  film  over  the  teeth,  and  in  many  mouths  patches  of 
gummy  material  collect  on  the  teeth  where  they  are  not 
cleaned  in  chewing  the  food  and  by  brushing.  These 
deposits  are  called  dental  plaques,  and  they  are  filled 
with  living  bacteria  that  produce  acid  and  start  decay 
beneath  the  plaques.  Tartar  is  a  hard  mineral  deposit 
that  usually  forms  most  abundantly  along  the  edge  of 
the  'gums.  It  is  often  stained  brown  by  the  escape  of 
blood  into  it  and  may  become  bluish,  green,  or  almost 
black  from  changes  in  the  coloring  matter  of  the  blood 
in  it. 

Thorough  brushing  of  the  teeth  helps  to  keep  them 
free  from  dental  plaques  and  tartar,  but  these  may  ap- 
pear on  places  where  the  brush  cannot  reach  them  or 


THE  TEETH  187 

even,  in  spite  of  the  most  careful  cleans:ng,  where  the 
brush  does  reach.  It  is  important,  therefore,  to  visit 
a  dentist  from  time  to  time  to  have  any  deposits  on 
the  teeth  removed. 

The  care  of  the  gums.  In  many  persons  the  gums  are 
slightly  inflamed  along  the  margins  and  bleed  easily 
when  they  are  brushed.  To  keep  them  in  health  it  is 
very  important  that  tartar  on  the  teeth  be  removed,  for 
the  tartar  irritates  the  gums  and  causes  them  to  shrink, 
leaving  the  roots  of  the  teeth  bare.  This  inflammation 
and  receding  of  the  gums  may  allow  germs  to  work 
down  about  the  roots  of  the  teeth  and  form  pus  about 
them,  thus  causing  them  to  become  loose  in  their  sockets. 
When  the  teeth  are  cleaned,  the  gums  should  also  be 
thoroughly  brushed  with  a  light,  quick  stroke  that  will 
stimulate  the  circulation  in  them  but  will  not  injure  them. 
One  dental  authority  states  that  inflamed  gums  can  be 
surely  restored  to  health  if  the  gums  and  teeth  are 
brushed  in  the  proper  manner  for  two  minutes  four  times 
a  day.  Some  writers  advise  that  in  cleaning  the  back 
teeth  the  brush  be  given  a  twisting  movement,  and  that 
the  brushing  be  always  from  the  gums  toward  the  crowns 
of  the  teeth.  Others  believe  that  the  outer  surfaces  of 
the  back  teeth  can  be  best  cleansed  by  giving  the  brush 
a  circular  or  rotatory  motion.  All  authorities  are  agreed 
that  the  brushing  should  not  be  crosswise  on  the  teeth. 
The  purpose  of  brushing  is  to  prevent  cavities  from 
forming  in  the  teeth  and  to  keep  the  gums  in  health,  and 
the  brushing  should  be  frequent  enough  and  thorough 
enough  to  accomplish  this  purpose.  It  is  best  to  have, 
two  tooth  brushes,  as  a  brush  becomes  soft  when  too 
frequently  used. 


1 88  PRIMER   OF  PHYSIOLOGY 

The  importance  of  visiting  the  dentist  frequently.  It 
is  very  important  that  the  teeth  be  inspected  by  a  den- 
tist at  regular  intervals  and  be  given  any  treatment 
they  may  need.  If  the  dental  plaques  are  not  removed, 
decay  may  start  beneath  them.  Tartar  that  is  not  re- 
moved irritates  the  gums  and  causes  them  to  become 
inflamed  and  to  shrink.  A  most  necessary  part  of  the 
care  of  the  teeth,  therefore,  is  to  have  any  deposits 
on  them  removed  promptly,  and  a  dentist  should  exam- 
ine the  teeth  every  three  months  to  see  if  this  needs  to 
be  done. 

It  is  also  important  that  cavities  be  filled  while  they 
are  yet  small,  both  because  this  plan  preserves  the  teeth 
and  because  it  is  more  economical  and  less  painful  than 
waiting  until  the  cavities  have  enlarged  and  a  great  part 
of  the  tooth  has  been  eaten  away.  All  over  the  land 
people  are  suffering  with  toothaches  and  paying  for  ex- 
pensive X-ray  work,  root  fillings,  and  crown  and  bridge 
work  when  they  could  have  preserved  their  teeth  by 
spending  a  mere  fraction  of  the  same  money  at  an  earlier 
date  for  small  fillings.  If  the  pulp  of  the  tooth  dies  and 
the  germs  gain  entrance  into  the  bones  of  the  jaw,  it  is 
exceedingly  difficult  to  eradicate  them  and  sometimes  it 
is  impossible  to  do  so.  It  is  not  considered  safe  to  fill  a 
dead  tooth  unless  the  X-ray  is  used  to  make  sure  that  the 
filling  extends  to  the  end  of  the  root  canals ;  even  after 
the  roots  are  filled  it  is  considered  advisable  to  put  a  tem- 
porary filling  in  the  tooth,  and  after  a  time  to  examine  it 
again  with  the  X-ray  to  make  sure  that  no  infection  has 
developed  in  the  bone  at  the  tips  of  the  roots.  Dental 
work  of  this  kind  is  very  expensive,  and  it  is  much  more 
satisfactory  to  have  the  teeth  attended  to  when  only 


THE   TEETH  189 

cleaning  and  small  fillings  are  required.  Unless  decayed 
teeth  can  be  so  treated  that  they  will  be  free  from 
germs,  it  is  better  to  have  them  extracted,  and  there  are 
not  a  few  dentists  who  believe  that  a  dead  tooth  is  better 
out  of  the  mouth  than  in  it. 

The  temporary  teeth.  The  jaws  are  too  small  in  child- 
hood to  hold  the  large  teeth  that  we  need  in  later  life. 
In  early  life  we  have,  therefore,  a  set  of  twenty  small 
temporary  teeth.  This  set  is  composed  of  four  incisors, 
two  canines,  and  four  molars  in  each  jaw  (Fig.  132). 
The  incisors  are  flat  and  chisel-like  for  biting  off  the 
food.  The  canines  are  more  round  and  pointed,  and  in 
the  dog  and  other  carnivorous  animals  they  are  used  as 
weapons  and  for  tearing  flesh.  The  molars  are  broad, 
square  teeth  with  square  cusps,  or  points,  and  wide  sur- 
faces for  crushing  and  grinding  the  food.  About  the 
sixth  year  the  temporary  teeth  begin  to  drop  out,  and 
by  the  twelfth  or  fourteenth  year  they  have  all  been 
replaced  by  permanent  teeth. 

The  permanent  teeth.     There  are  thirty-two  perma- 
nent teeth.     In  each  jaw  there  are  four  incisors   and 
two  canines  that  replace 
the  incisors  and  canines 
of   the  temporary  teeth  ; 
four  bicuspids  in  place  of 
the    temporary    molars  ; 

and  Six  molars  that  Come  FIG.  131.    The  tooth  on  the  right  de- 

in  behind  the  Space  OCCU-  cayed.  the  roots  were  not  absorbed,  and 

.     ,     .  the  tooth  had  to  be  pulled  to  make  room 

pied     by     the     temporary  for  the  permanent  tooth.    The  tooth  in 

teeth.       The    first    perm  a-  the  middle    shows  the  roots  partly  ab- 


nent  molars  appear  about    f0/*-  Jhe  roots  f  *e  <ooth  ™    ! 

r  _  left  have  been  completely  absorbed  and 

the  sixth  year.    The  third    the  tooth  has  dropped  out. 


1 90 


PRIMER    OF  PHYSIOLOGY 


incisors   5~8 
canine 

molars 


molars,  or  wisdom  teeth,  usually  appear  from  the  six- 
teenth to  the  twenty-first  year,  but  in  some  persons  these 
teeth  never  make  their  way  through  the  gums.1 

The  importance  of  caring  for  the  temporary  teeth.     The 
first  reason  for  caring  for  the  temporary  teeth  is  that 

they  themselves  are  nec- 
essary for  the  health  ;  for 
if  they  are  allowed  to  de- 
cay, the  child  will  form 
the  habit  of  bolting  his 
food  ;  the  digestion  will 
be  deranged  by  the  germs 
that  are  swallowed  ;  and 

FIG.  132.    The  upper  temporary  teeth  of 

a  child  about  three   years   old  with  the     tne  nerVOUS  System   and 

average  time  of  eruption  given  in  months,     the    disposition     will    be 

• 

weeks  earlier  than  the  upper.  The  first 
permanent  molars,  which  at  trlis  time  are 
being  formed  in  the  jaws,  are.  shown  be- 
hind  the  temporary  teeth. 


20-32 


j  j     •>          .-, 

damagec      bY 

from  the   toothache  that 

{-foe    child    will    be     COm- 

„     -  ._, 

pelled  to  endure.  For 
the  sake  of  the  health  during  the  years  of  -childhood  and 
to  prevent  the  forming  of  wrong  eating  habits,  the  tem- 
porary teeth  should  have  the  best  of  care. 

The  second  reason  for  caring  for  the  temporary  teeth 
is  to  prevent  the  permanent  teeth  from  coming  in  irreg- 
ularly. The  permanent  teeth  begin  to  form  long  before 

1  Sometimes  when  the  wisdom  teeth  or  other  teeth  fail  to  appear  at  the 
normal  time  it  is  because  they  have  turned  sideways  in  the  jaw  or  have 
become  tightly  wedged  among  the  roots  of  the  other  teeth.  Teeth  that 
are  lodged  in  the  jaw  in  this  way  are  called  impacted  teeth,  and  there  are 
many  cases  on  record  of  persons  who  suffered  greatly  from  nervous  troubles 
because  of  the  pressure  such  teeth  were  exerting.  If  the  teeth  do  not  ap- 
pear at  the  proper  time  and  there  is  any  trouble  with  the  health,  impacted 
teeth  should  be  looked  for.  The  X-ray  is  used  in  making  the  examination. 


THE  TEETH 


birth  at  the  roots  of  the  temporary  teeth,  and  by  the  end 
of  the  third  year  even  the  wisdom  teeth  are  formed  in 
the  jaws.  These  teeth  then  gradually  grow  and  harden, 
and  the  roots  of  the  temporary  teeth  disappear  before 
them  (Fig.  131).  Finally,  the  roots  of  the  temporary 
teeth  are  entirely  absorbed  and  the  first  teeth  drop  out, 
leaving  the  places  they  occupied  to  the  permanent  teeth. 
If  the  temporary 

""      7-9 


incisors 
canine 


bicuspids 


molars 


FIG.  133.  The  upper  permanent  teeth  of  a  man 
twenty-six  years  old,  with  the  average  time  of 
eruption  given  in  years.  The  lower  teeth  usu- 
ally appear  two  or  three  months  earlier  than  the 
corresponding  upper  ones. 


teeth  are  allowed  to 
decay,  their  roots  are 
not  absorbed  before 
the  permanent  teeth. 
The  second  teeth, 
therefore,  either  re- 
main buried  in  the 
jaws  or  appear  in  an 
irregular  line,  some 
inside  and  some  out- 
side of  the  line  of  the 
first  teeth.  Another 
difficulty  caused  by  decay  and  loss  of  the  temporary 
molars  is  that  when  the  first  permanent  molars  come  in 
they  move  forward  and  take  positions  that  belong  to  the 
bicuspids  and  there  is  then  not  enough  room  for  the  per- 
manent bicuspids.  For  the  sake  of  the  permanent  teeth, 
therefore,  the  temporary  set  should  have  the  best  dental 
care,  and  if  for  any  reason  they  have  been  allowed  to  de- 
cay, a  dentist  should  be  consulted  when  it  is  time  for  the 
second  teeth  to  appear.  Permanent  fillings  and  not 
cement  fillings  should  be  used  in  the  temporary  teeth, 
for  some  of  these  teeth  remain  in  the  mouth  until  the 
child  is  10  or  12  years  of  age. 


192 


PRIMER   OF  PHYSIOLOGY 


canine 


incisors 


incisors 


bicuspids 
first  molar 


canine 


first 
molar 


bicuspids 

FIG.  134.  The  jaws  of  a  child  four  years 
old.  The  jaw-bones  have  been  cut  away  to 
show  the  permanent  teeth  growing  at  the 
roots  of  the  temporary  set. 


The  importance  of  caring  for  the  first  permanent  molars. 

The  first  permanent  teeth,  which  come  in  about  the  sixth 

year,  behind  the  tem- 
porary molars,  are  of- 
ten mistaken  for  tem- 
porary teeth.  These 
molars  have  deep 
grooves  in  their  sur- 
faces in  which  the  food 
lodges,  and  they  come 
into  the  mouths  of 
many  children  before 
the  habit  of  washing 
the  teeth  has  been 
formed.  They  are  therefore  especially  liable  to  decay. 
They  should  be  filled  at  once  if  cavities  appear  in  them, 
because  they  are  not  replaced  when  lost,  and  without 
them  the  jaws  do  not  grow  in  length  as  they  should. 
Count  the  double  teeth  in  the  mouth  of  a  six-  or  seven- 
year-old  child,  and  if  there  are  three  of  them  on  one  side 
of  the  jaw,  the  back  one  is  a  permanent  molar. 

Other  points  in  the  care  of  the  teeth.  Sticky  foods  like 
oatmeal  and  mashed  potatoes  cling  to  the  teeth  and  cause 
them  to  decay.  Hard  foods  like  apples,  cornbread,  and 
bacon  clean  the  teeth  and  give  the  gums  the  exercise 
that  is  needed  to  keep  up  the  circulation  through  them. 
Every  diet,  therefore,  should  contain  some  tough,  solid 
material  into  which  the  eater  can  set  his  teeth.  Sugar 
left  among  the  teeth  ferments  easily  and  causes  decay. 
For  this  reason  eating  candy  at  all  hours  of  the  day,  so 
that  the  crevices  among  the  teeth  are  kept  filled  with 
it,  is  almost  sure  to  cause  decay. 


THE   TEETH  193 

Straightening  irregular  teeth.  Often  the  permanent 
teeth  come  in  irregularly  and  are  turned  forward  in 
front  because  the  temporary  teeth  have  been  allowed  to 
decay  or  because  adenoids  or  nasal  growths  have  kept 
the  bones  of  the  jaws  and  of  the  roof  of  the  mouth 
from  growing  enough  to  make  room  for  the  teeth. 
When  for  these  or  any  other  reasons  the  teeth  are  ir- 
regular, a  dentist  who  understands  how  to  straighten 
them  should  at  once  be  consulted.  By  putting  pressure 
on  the  teeth  the  bones  may  be  made  to  grow  larger  and 
the  arch  of  the  jaw  ex- 
panded until  the  teeth 
have  sufficient  room. 

Figure  136  gives  an 
idea  of  the  changes 
that  a  good  dentist 

0     %  FIG.  135.    This  shows  how  the  upper  teeth 

Can    make    in    the    ap-      should  close  on  the  lower  teeth.     (After  a 


Of    a  person       photograph  from    "  The    Practical    Ortho- 
,  ,  ,  dentist") 

whose      mouth     is 

spoiled  by  irregular  or  protruding  teeth.  The  work  of 
straightening  the  permanent  teeth  ought  to  be  begun 
as  soon  as  they  appear,  and  not  delayed  until  all  of  them 
are  in  the  mouth,  as  is  often  advised.  A  tooth  that  has 
been  crowded  out  of  line  ought  not  to  be  pulled,  but  the 
circle  of  the  teeth  should  be  widened  until  there  is  room 
for  all. 

Defective  teeth  due  to  illness  and  to  lack  of  calcium 
in  the  diet.  A  tooth  is  first  built  up  by  the  growth  of 
a  "bud,"  or  little  group  of  cells  of  the  mucous  mem- 
brane which  covers  the  jaw.  It  is  then  hardened  by 
having  calcium  deposited  in  it.  This  hardening  of  the 
teeth  is  going  on  all  through  childhood,  and  severe  cases 


194 


PRIMER   OF  PHYSIOLOGY 


of  scarlet  fever,  measles,  diphtheria,  and  other  illnesses 
may  interfere  with  the  deposition  of  lime  and  cause  the 
teeth  to  be  soft  and  ilHormed  when  they  come  through 
the  gums  months  or  years  later. 

Defective  teeth  may  also  be  caused  by  lack  of  cal- 
cium in  the  diet,  as  we  have  already  pointed  out  (page 
140).  It  is  therefore  especially  important  to  the  teeth 


FlG.  136.    Two  cases  in  which  the  teeth  needed  and  received  the  care  of  a 
good  dentist.     {After  a  photograph  from  "  The  Practical  Orthodontist.") 

that  children  be  guarded  from  disease  and  that  an  abun- 
dance of  lime  be  supplied  in  the  food  during  the  early 
years  of  life.  The  question  of  lime  in  the  diet  should 
be  given  special  care  when  babies  are  brought  up  on 
any  food  other  than  milk. 

Care  of  the  mouth  of  an  infant.  Little  babies  often 
suffer  from  sore  mouth.  This  disease  is  caused  by 
germs  and  is  usually  brought  on  by  lack  of  cleanliness. 
It  should  be  promptly  attended  to  by  a  physician,  be- 
cause it  not  only  causes  suffering  and  nervousness  in 
the  child  but  also  fills  the  alimentary  canal  with  germs 


THE  TEETH  195 

and  ruins  the  digestion.  When  the  teeth  are  making 
their  way  through  the  gums,  the  mouth  should  be  ex- 
amined to  see  that  there  are  no  little  ulcers  on  the  gums 
when  the  teeth  are  cutting  through.  If  these  are  found 
a  physician  or  a  dentist  should  be  consulted ;  for  it  is 
very  unwise  to  allow  a  child  to  go  on  swallowing  the 
many  thousands  of  pus-forming  germs  that  come  from 
the  ulcers.  One  of  the  best  means  of  preventing  trouble 
in  the  mouth  of  a  baby  is  to  wipe  out  the  mouth,  after 
feeding,  with  a  clean  cloth  that  has  been  dipped  in  a  sat- 
urated solution  of  borax  or  boric  acid. 

Decayed  teeth  very  common.  Among  the  846  children 
examined  in  a  school  in  Cleveland,  Ohio,  only  three 
had  perfect  teeth.  Examinations  of  many  thousands  of 
other  children  show  that  often  as  many  as  95  per  cent 
of  them  are  in  need  of  dental  care.  The  great  majority 
of  young  persons  lose  their  first  permanent  molars  before 
they  are  twenty  years  of  age,  and  it  is  undoubtedly  true 
that  no  other  part  of  the  body  is  so  often  defective  as 
the  teeth.  You  should  be  on  guard,  therefore,  to  pre- 
serve the  precious  heritage  which  nature  has  given  you 
in  the  form  of  your  teeth  ;  for  your  chances  of  health  in 
later  years  depend  very  largely  on  the  care  that  you  give 
your  teeth  now.  Keep  them  clean  by  all  means,  and 
if  there  are  small  cavities  in  them,  have  them  filled  at 
once.  v 

QUESTIONS 

In  what  two  ways  do  bad  teeth  injure  the  health  ?  •  Name 
the  parts  of  a  tooth.  Of  what  is  the  body  of  a  tooth  com- 
posed? With  what  is  the  crown  covered?  How  may  the 
enamel  be  injured?  What  results  usually  follow  breaking 


196  PRIMER   OF  PHYSIOLOGY 

the  enamel  ?  How  are  the  teeth  fastened  in  the  sockets  ? 
Where  is  the  pulp  cavity  ?  What  does  it  contain  ? 

What  causes  decay  of  the  teeth  ?  What  happens  if  the  decay 
continues  until  the  pulp  is  reached  ?  How  may  decay  be  pre- 
vented? Why  should  particles  of  food  that  lodge  between 
the  teeth  be  removed?  How  may  a  good  tooth  powder  be 
made  ?  Why  should  gritty  substances  not  be  used  to  clean 
the  teeth  ?  What  kind  of  brush  is  best  for  cleaning  the  teeth  ? 

What  are  dental  plaques  ?  What  is  tartar  ?  Give  two 
important  points  in  keeping  the  gums  in  health.  How  should 
the  brush  be  used  in  cleaning  the  teeth  ?  How  often  should 
the  teeth  be  brushed  ? 

Why  is  it  important  to  visit  the  dentist  regularly  ?  Why 
should  dental  plaques  be  removed?  Why  should  tartar  be 
removed  ?  Explain  why  it  is  important  to  have  all  cavities 
filled  while  they  are  small. 

How  many  teeth  are  there  in  the  temporary  set  ?  Name 
and  describe  the  different  kinds.  How  many  teeth  are  there 
in  the  permanent  set  ?  When  does  the  first  permanent  molar 
appear  ?  Give  two  reasons  for  caring  for  the  temporary  teeth. 
Why  are  the  first  permanent  molars  especially  liable  to  decay  ? 
Why  is  their  loss  harmful  ? 

Why  are  hard  foods  better  for  the  teeth  than  sticky  foods  ? 
Why  is  constant  candy  eating  injurious  ?  How  do  adenoids 
and  nasal  growths  affect  the  teeth  ?  What  should  be  done 
when  the  teeth  are  crooked  ?  How  may  illness  during  child- 
hood injure  the  teeth  ?  What  element  needed  for  building 
the  teeth  is  sometimes  lacking  in  the  diet  of  children  ? 

When  babies  have  sore  mouth,  what  is  usually  the  cause  ? 
What  trouble  should  be  guarded  against  while  the  teeth  are 
coming  through  the  gums?  HOW  can  trouble  in  a  baby's 
mouth  be  prevented? 

Cite  some  facts  to  show  how  common  defective  teeth  are. 


CHAPTER   TWENTY 

TOBACCO 


FIG.  137.    The  peace  pipe. 

WHEN  Columbus  returned  from  the  West  Indies,  he 
reported  that  the  natives  carried  with  them  to  kindle  fires 
a  brand  made  by  rolling  in  corn  husks  the  leaves  of  a 
certain  herb  which  they  cultivated.  He  also  reported 
that  they  perfumed  themselves  with  the  leaves  of  this 
herb,  and  that  no  treaty  of  peace  could  be  ratified  among 
the  Indians  without  smoking  the  herb  in  a  pipe,  because 
they  believed  that  when  the  smoke  of  its  burning  as- 
cended to  heaven  the  Great  Spirit  smelled  a  sweet  savor 
and  was  pleased. 

The  use  of  this  Indian  herb  became  popular  in  England 
through  the  influence  of  Sir  Walter  Raleigh,  and  the 
custom  of  using  it  spread  rapidly  through  Europe  in 
the  seventeenth  century.  At  first  it  was  thought  to  have 
medicinal  value,  but  in  a  short  time  men  of  intelligence 
and  high  position  came  to  think  of  it  as  a  dangerous 
drug  and  became  alarmed  as  to  the  consequences  that 

197 


198  PRIMER    OF  PHYSIOLOGY 

would  follow  its  widespread  use.1  A  great  movement 
against  the  new  custom  then  sprang  up  over  all  the 
known  world.  In  Turkey  the  pipes  of  smokers  were 
thrust  through  their  noses ;  in  Russia  the  noses  of 
smokers  were  cut  off,  and  those  who  repeated  the  offense 
were  put  to  death ;  the  church  threatened  the  users  of 
the  weed  with  excommunication ;  and  King  James  of 
England  issued  a  protest  against  its  use,  in  which  he 
declared  it  to  be  "  a  custom  loathsome  to  the  eye,  hate- 
ful to  the  nose,  harmful  to  the  brain,  dangerous  to  the 
lungs,  and  in  the  black,  stinking  fume  thereof  nearest 
resembling  the  horrible  Stygian  smoke  of  the  pit  that  is 
•  bottomless." 

Why  the  habit  of  using  tobacco  is  so  widespread.  In 
spite  of  all  the  opposition  that  has  been  offered  to  it, 
tobacco  is  now  used  over  practically  the  whole  world. 
In  the  United  States  the  people  spend  for  it  more  than 
four  hundred  millions  of  dollars  yearly.  Of  course, 
if  people  spend  their  money  in  this  way,  it  means 
that  they  will  be  compelled  to  go  without-food,  clothing, 
furniture,  books,  music,  and  other  things  that  for  their 
health,  comfort,  and  richness  of  life  they  ought  to  have  ; 
it  means  millions  of  extra  years  of  labor  for  a  people 
who  are  already  overworked.  In  India  all  ages  and 
both  sexes  are  constant  smokers,  and  in  China  many  of 
the  workmen  carry  with  them  as  their  constant  compan- 

1  During  the  seventeenth  century  the  plague,  or  "  Black  Death," 
ravaged  Europe,  and  it  was  generally  believed  that  smoking  was  a  safe- 
guard against  this  disease.  It  is  possible  that  there  was  some  foundation 
for  this  belief ;  for  the  plague  is  spread  by  fleas  that  come  from  plague- 
infected  rats,  and  it  may  be  that  fleas  dislike  the  odor  of  tobacco  that  is 
present  on  the  clothes  and  skin  of  tobacco  users. 


TOBACCO  199 

ions  a  supply  of  tobacco  and  a  pipe.  Yet  in  Inch* a  and 
in  China  the  great  mass  of  the  people  toil  for  a  miserable 
wage  that  will  hardly  keep  them  alive,  and  in  years  of 
crop  failure  hundreds  of  thousands  of  them  actually 
perish  for  lack  of  food. 

Why  do  men  put  this  extra  burden  on  themselves  ? 
Why  did  the  Indians  that  Columbus  saw  perfume  them- 
selves with  the  odor  of  tobacco  ?  Why  do  men  now 
engage  in  the  seemingly  foolish  custom  of  drawing 
smoke  into  the  mouth  and  puffing  it  out  again  ?  Let 
us  search  out  the  answer  to  this  problem. 

Nicotin.  There  are  certain  drugs  that  produce  such 
pleasurable  effects  on  the  mind  that  people  form  the 
habit  of  taking  them  to  experience  these  effects.  Among 
these  drugs  may  be  mentioned  hasheesh,  which  comes 
from  Indian  hemp  and  is  used  by  the  people  of  India. 
It  produces  a  kind  of  intoxication  and  fills  the  mind 
with  the  most  brilliant  ideas  of  grandeur  and  power, 
causing  the  most  pitiful  specimen  of  humanity  to  feel 
himself  a  very  king  among  men.  Alcohol  has  something 
of  this  same  effect,  for  it  deadens  the  judgment  and  the 
critical  powers  of  the  mind  and  causes  a  person  to  regard 
his  own  efforts  as  brilliant,  even  when  there  is  no  ground 
for  a  high  opinion  of  what  he  has  done.  Opium  deadens 
the  sensibilities  to  pain  and  produces  sensations  of  de- 
licious ease  and  luxury.  Cocain,  chloral,  and  a  few 
other  drugs  produce  effects  that  are  pleasant  to  the 
mind,  and  men  fall  into  the  habit  of  taking  them.  The 
most  widely  used  of  all  these  drugs,  however,  is  nicotin, 
which  is  present  in  tobacco.  The  sensations  produced 
by  it  will  be  discussed  in  a  later  paragraph. 

Nicotin  a  narcotic.     Physicians  speak  of  certain  drugs 


200  PRIMER   OF  PHYSIOLOGY 

as  stimulants  and  of  certain  others  as  narcotics.  Stimu- 
lants quicken  the  action  of  the  protoplasm  of  the  cells ; 
they  make  the  muscles  contract  more  strongly  and 
cause  the  nervous  system  to  conduct  impulses  better 
and  to  control  the  body  with  a  firmer  hand.  Narcotics 
deaden  the  nervous  system  and  weaken  its  action ;  they 
slacken  the  muscles  and  lessen  their  strength.  Strych- 
nin is  a  good  example  of  a  stimulant.  It  is  given  by 
physicians  when  the  heart  action  flags  and  when  there 
is  general  weakness  and  collapse.  Opium  is  an  example 
of  a  narcotic.  It  is  given  by  physicians  to  dull  the 
senses  to  pain  and  to  quiet  those  whose  nervous  sys- 
tems have  been  overwrought.  The  nicotin  that  is  in 
tobacco  is  a  narcotic,  and  it  is  so  strong  that  a  few  drops 
of  it  introduced  into  the  mouth  will  paralyze  the  nervous 
system  and  stop  the  beating  of  the  heart.1  We  shall 
now  discuss  some  of  the  more  important  effects  of 
nicotin  on  the  body. 

The  influence  of  tobacco  on  growth.  There  are  many 
indications  that  the  processes  within  the  cells  that  cause 
growth  differ  from  the  processes  that  go  on  during  the 
repair  of  the  protoplasm.  That  is,  in  cells  and  in 
young  people  that  are  growing,  there  are  processes 
going  on  that  are  not  going  on  in  cells  and  in  persons 

1  Tobacco  is  from  I  to  4  per  cent  nicotin.  In  chewing,  only  a  small 
part  of  the  nicotin  in  the  tobacco  is  absorbed  into  the  body,  and  in 
smoking,  most  of  the  nicotin  is  broken  into  other  compounds.  It  is 
probable  that  these  other  compounds  produce  a  large  part  of  the  effect 
that  follows  smoking.  That  men  smoke  to  obtain  the  drug  effects  of 
nicotin  and  of  the  compounds  that  come  from  the  nicotin,  and  not  for 
the  physical  and  mental  pleasure  of  the  smoking,  is  shown  by  the  fact  that 
a  smoker  is  not  satisfied  with  tobacco  from  which  the  nicotin  has  been 
extracted. 


TOBACCO  201 

that  have  reached  their  full  size.1  Tobacco  seems  to 
have  an  especially  evil  effect  on  the  processes  of 
growth  ;  for  without  doubt  it  is  most  injurious  to  the 
young.  Two  young  guinea  pigs  that  were  made  to 
inhale  tobacco  smoke  from  the  fourth  day  after  birth, 
on  the  forty-fourth  day  weighed  174  and  169  grams 
respectively  instead  of  330  grams,  which  is  the  normal 
weight  for  a  guinea  pig  of  this  age.  One  of  them  died 
on  the  forty-fourth  day,  and  the  other  was  not  subjected 
to  further  inhalations.  At  the  end  of  the  third  month 
this  animal  weighed  only  295  grams.  The  normal 
weight  at  that  age  is  485  grams,  so  the  animal  was  still 
stunted  and  far  below  its  normal  size. 

So  generally  is  it  known  that  cigarette  smoking  inter- 
feres with  the  processes  of  growth  and  stunts  the  young 
that  most  of  our  states  have  laws  forbidding  the  sale  of 
cigarettes  to  boys  below  a  certain  age.  In  1889  the 
Japanese  government  became  alarmed  because  of  the 
small  size  of  some  of  its  citizens,  and  after  an  investi- 
gation of  the  effects  of  tobacco  passed  a  law  which 
was  worded  thus :  "  Smoking  of  tobacco  by  persons 
under  the  age  of  twenty  is  prohibited."  Professor 
Seaver  of  Yale  University  found  that  of  the  young  men 
entering  Yale  during  a  period  of  ten  years,  the  smokers 
averaged  15  months  older  than  the  non-smokers,  and 
that  notwithstanding  their  greater  age  they  were  one 
third  of  an  inch  shorter  and  had  slightly  less  lung  capac- 
ity. The  boy  who  wishes  to  become  large  and  strong 

1  By  experiments  on  animals  it  has  been  found  possible  to  feed  them 
in  a  way  that  will  keep  them  alive,  but  will  not  cause  growth  in  them. 
This  indicates  that  the  processes  of  growth  and  of  maintenance  are 
different. 


202  PRIMER   OF  PHYSIOLOGY 

should  let  cigarettes  alone  during  his  growing  years,  for 
there  is  every  reason  to  believe  that  young  smokers  fail 
to  reach  their  full  development  either  of  body  or  of  mind. 

The  effect  of  tobacco  on  the  muscles.  As  we  should 
expect,  tobacco  weakens  and  relaxes  the  muscles.  Pro- 
fessor Lombard  of  the  University  of  Michigan  tested 
the  strength  and  endurance  of  his  finger  muscles  on 
four  days  on  which  he  smoked  five  cigars  daily;  then 
on  four  days  on  which  he  abstained  from  smoking; 
then  again  on  four  days  when  he  smoked  as  on  the  first 
days.  He  found  that  on  the  days  he  smoked,  his 
muscles  had  lost  on  an  average  41  per  cent  of  their 
working  power. 

The  fact  that  tobacco  softens  and  slackens  the 
muscles  was  so  well  known  before  the  days  of  chloro- 
form that  patients  were  prepared  for  certain  surgical 
operations  by  giving  them  tobacco  to  bring  about  a 
relaxed  condition  of  the  muscles.  At  the  present  time, 
it  is  well  known  among  athletes  that  smoking  lowers 
the  strength,  and  athletes  who  are  in  training  are  not 
allowed  to  indulge  in  tobacco.  Cigarettes  will  surely 
kill  the  baseball  pitcher's  speed ;  they  shorten  the  flight 
of  the  football  player's  punt ;  and-  the  tobacco  user's 
muscles  weaken  and  fail  when  the  crowning  effort  of  the 
race  comes. 

The  effect  of  tobacco  on  the  nervous  system.  The 
most  serious  effects  of  tobacco  are  on  the  nervous  sys- 
tem. It  interferes  with  the  control  of  the  muscles,  and 
it  damages  the  mind,  as  we  should  expect  a  narcotic  to 
do.  The  trembling  that  may  be  seen  in  the  hands  of 
almost  any  one  who  smokes  cigarettes  to  excess  shows 
in  a  very  marked  way  how  tobacco  interferes  with 


TOBACCO  203 

the  control  of  the  muscles.  Because  of  this  effect, 
tobacco  users  are  not  good  marksmen  with  the  rifle, 
and  many  of  them  are  unable  to  do  delicate  work.  The 
following  statement  by  Luther  Burbank,  the  great 
plant  breeder  and  nurseryman  of  California,  illustrates 
this  point: 

"  To  assist  me  in  my  work  of  budding  —  work  that  is 
as  accurate  and  exacting  as  watch  making  —  I  have  a 
force  of  some  twenty  men.  I  discharge  men  from  this 
force  at  the  first  show  of  incompetency.  Some  time 
ago  my  foreman  asked  me  if  I  took  pains  to  inquire  into 
the  habits  of  my  men.  On  being  answered  in  the  nega- 
tive, he  surprised  me  by  saying  that  the  men  I  found 
unable  to  do  the  delicate  work  of  budding  invariably 
turned  out  to  be  smokers  and  drinkers.  These  men, 
while  able  to  do  the  rough  work  of  farming,  call  budding 
and  other  delicate  work  '  puttering  '  and  have  to  give  it 
up,  owing  to  inability  to  concentrate  their  nerve  force. 
Even  men  who  smoke  one  cigar  a  day  I  cannot  intrust 
with  some  of  my  delicate  work." 

The  effect  of  tobacco  on  the  mind  is  even  more  notice- 
able than  its  effect  on  muscular  control.  A  study  of  the 
grades  of  500  boys  in  private  schools  shows  that  the 
grades  of  smokers  were  on  an  average  12  to  15  per  cent 
lower  than  the  grades  of  non-smokers.  Another  set  of 
statistics  covering  sixteen  schools  in  different  parts  of 
the  country  and  including  800  boys  showed  that  the 
smokers  had  fallen  on  an  average  17  to  28  per  cent 
behind  those  who  did  not  use  the  drug.  A  comparison 
of  50  smokers  and  50  non-smokers  chosen  at  random 
in  Kansas  State  Agricultural  College  showed  that  the 
smokers  had  averaged  28  per  cent  lower  in  grades  and 


204  PRIMER   OF  PHYSIOLOGY 

that  they  had  made  74  per  cent  of  all  the  failures  that 
were  made  by  the  100  boys. 

Many  other  comparisons  of  the  scholarship  records  of 
tobacco  users  and  non-tobacco  users  have  been  made, 
and  in  every  case  the  tobacco  users  stand  far  below  the 
others  in  scholarship.  So  well  known  is  it  that  tobacco 
interferes  with  good  intellectual  work  that  many  large 
corporations  absolutely  refuse  to  take  into  their  employ 
young  men  who  use  cigarettes.  Judge  Stubbs  of  Indiana 
gives  a  list  of  twenty-two  great  employers  who  follow 
this  rule.  The  list  includes  Marshall  Field  &  Co.,  John 
Wanamaker,  and  seven  great  railroads. 

How  tobacco  affects  the  mind.  Tobacco  undoubtedly 
injures  the  mind,  so  that  the  person  using  it  learns  less 
rapidly  and  thinks  less  clearly.  Those  who  have  used 
it  for  some  time  have  a  tendency  to  become  nervous, 
restless,  unable  to  remain  still  for  any  length  of  time, 
and  unable  to  keep  their  minds  concentrated  on  any 
one  subject.  As  one  writer  expresses  it,  "  The  mind  of 
a  tobacco  user  seems  to  lose  its  grasp  of -things."  It  is 
probable,  however,  that  the  main  reason  why  tobacco 
users  fall  behind  other  men  in  intellectual  work  is  that 
nicotin  steals  away  ambition.  Its  first  effect  on  the 
mind  is  to  lull  it  to  rest ;  to  make  one  contented  with 
himself  and  his  achievements ;  to  make  one  satisfied  to 
sit  and  watch  the  smoke  curl  upward  while  other  things 
take  care  of  themselves.1  This  feeling  of  ease,  comfort, 
and  freedom  from  responsibility  is  very  pleasurable,  and 
the  tobacco  habit  is  the  most  common  of  all  the  drug 
habits  to  which  man  is  addicted.  In  summing  up  the 

1  "Under  the  influence  of  tobacco,  thought  becomes  reverie."  — 
VICTOR  HUGO. 


TOBACCO  205 

good  or  the  evil  which  comes  from  a  habit  of  this  kind, 
however,  we  must  always  remember  that  the  world's 
work  must  be  done,  and  that  when  a  drug  .for  any  rea- 
son interferes  with  the  working  powers  of  a  man,  some 
one  else  will  probably  be  compelled  to  do  the  work 
which  he  ought  to  have  done.  We  must  also  remember 
in  connection  with  all  drug  habits  that  it  is  important 
to  know  whether  we  are  to  be  forced  to  pay  with  the 
health  of  our  cells  for  the  pleasurable  sensation  that 
the  drug  gives. 

Other  effects  of  tobacco  on  the  body.  Dyspepsia  is 
very  common  among  tobacco  chewers  who  swallow  small 
quantities  of  the  juice  and  among  those  who  damage  their 
nervous  systems  by  excessive  smoking.  Another  effect 
of  the  continued  use  of  tobacco  is  to  raise  the  blood 
pressure^  which  greatly  increases  the  work  of  the  heart. 

Smoking  also  has  a  bad  effect  on  the  air  passages ; 
for  the  hot  ammonia  and  other  compounds  in  the  smoke 
frequently  cause  "smoker's  sore  throat,"  and  cancer 
of  the  tongue  and  throat  is  more  common  among 
smokers  than  among  non-smokers.  Besides  all  these 
effects  on  separate  organs  of  the  body,  the  nicotin  has 
a  depressing  and  weakening  effect  on  the  body  as  a 
whole,  just  as  it  has  an  enfeebling  and  quieting  effect 
on  the  mind. 

The  effect  of  a  moderate  use  of  tobacco.  In  reading 
this  chapter  you  must  bear  in  mind  that  not  all  the  evil 
effects  of  tobacco  that  have  been  described  come  at 
once,  nor  is  it  possible  to  observe  all  of  them  in  every 
person  who  is  a  tobacco  user.  Small  doses  of  any  drug 
produce  proportionately  smaller  effects  than  do  larger 
doses,  so  persons  who  use  tobacco  moderately  suffer 


206  PRIMER   OF  PHYSIOLOGY 

less  from  it  than  do  persons  who  use  large  amounts. 
The  superintendent  of  the  reform  school  at  Westboro, 
Massachusetts,  says,  "  All  boys  sent  here  have  been 
users  of  tobacco."  The  chief  probation  officer  of  the 
juvenile  court  of  Washington,  D.C.,  says,  "  In  dealing 
with  more  than  16,000  delinquent  children  of  this  city 
during  the  last  eight  years,  I  find  as  a  rule  that  the  user 
of  cigarettes  is  a  stunt,  a  weakling  in  body,  mind,  and 
morals."  In  Chicago,  of  2402  cigarette  smokers  in  the 
grades  below  the  high  school,  only  6  per  cent  were 
doing  their  school  work  well  enough  to  pass. 

These  are  the  effects  of  tobacco  when  used  to  excess 
or  when  used  by  the  young,  and  persons  who  have 
experience  with  cases  of  this  kind  naturally  regard 
tobacco  as  one  of  the  worst  enemies  of  mankind. 
Others  who  see  men  all  about  them  smoking  and  yet 
attending  to  their  work  day  by  day  often  take  the  view 
that  after  all  the  tobacco  habit  is  of  little  consequence. 
The  truth  is  that  some  men  are  born  with  more  health, 
strength,  ambition,  and  intelligence  than  others,  and 
that  one  of  these  strong  men,  even  after  using  tobacco 
for  a  long  time,  may  still  have  more  strength  and  brain 
power  than  the  man  who  lacked  these  qualities  from 
his  birth. 

The  question  is  not,  however,  whether  the  strongest 
tobacco  user  has  more  strength  than  the  weakest  man 
who  does  not  use  tobacco.  The  question  is  whether  the 
strong  man  is  able  to  use  tobacco  and  at  the  same  time 
realize  the.  full  strength  of  his  body  and  of  his  mind. 
Everything  that  we  know  about  the  effect  of  nicotin 
indicates  that  it  is  not  possible  to  do  this ;  that  it  is  a 
violent  poison  to  the  cells ;  that  if  taken  into  the  body 


TOBACCO  207 

in  large  amounts,  it  will  cause  death ;  that  if  constantly 
taken  during  the  growing  years,  it  has  a  very  disastrous 
effect  on  development ;  that  in  any  amount  whatsoever  it 
has  a  narcotic  effect  on  the  muscles  and  on  the  delicate 
cells  of  the  brain  ;  and  that  any  one  who  uses  it  will  be 
damaged  by  it. 

Why  a  boy  should  not  use  tobacco.  "  Your  first  duty 
in  life  is  toward  your  afterself- — the  man  you  ought  to 
be.  So  live  that  he  in  his  time  may  be  possible  and 
actual. 

"  Far  away  in  the  years  he  is  waiting  his  turn.  His 
body,  his  brain,  his  soul,  are  in  your  boyish  hands.  He 
cannot  help  himself. 

"  What  will  you  leave  for  him  ? 

"  Will  it  be  a  brain  unspoiled  by  lust  or  dissipation,  a 
mind  trained  to  think  and  act,  a  nervous  system  true  as 
a  dial  in  its  response  to  the  truth  about  you  ?  Will  you, 
Boy,  let  him  come  as  a  man  among  men  in  his  time  ? 
Or  will  you  throw  away  his  inheritance  before  he  has 
had  the  chance  to  touch  it  ?  Will  you  turn  over  to  him 
a  brain  distorted,  a  mind  diseased,  a  will  untrained  to 
action  ? 

"  Will  you  let  him  come,  taking  your  place,  gaming 
through  your  experiences,  hallowed  through  your  joys ; 
building  on  them  his  own  ? 

"  Or  will  you  fling  away  his  hope,  decreeing  wanton- 
like  that  the  man  you  might  have  been  shall  never  be  ? 

"  This  is  your  problem  in  life ;  the  problem  of  more 
importance  to  you  than  any  or  all  others.  How  will 
you  meet  it,  as  a  man  or  as  a  fool  ? 

"  When  you  answer  this,  we  shall  know-  what  use  the 
world  can  make  of  you."  —  DAVID  STARR  JORDAN. 


208  PRIMER   OF  PHYSIOLOGY 

QUESTIONS 

Tell  of  the  discovery  of  tobacco  and  its  introduction  into 
Europe.  What  different  opinions  were  at  first  held  about  to- 
bacco? Name  some  drugs  that  are  commonly  used  for  their 
pleasant  effects.  What  effect  has  a  stimulant?  a  narcotic? 
Is  nicotin  a  stimulant  or  a  narcotic  ? 

At  what  time  of  life  is  tobacco  especially  injurious?  De- 
scribe the  experiment  in  which  young  guinea  pigs  were  made 
to  inhale  tobacco  smoke.  Why  do  most  of  our  states  prohibit 
the  sale  of  cigarettes  to  young  persons  ?  Give  the  results  of 
Professor  Seaver's  observations  on  students  in  Yale  University. 

What  effect  has  tobacco  on  the  muscles?  Describe  the 
experiment  performed  by  Professor  Lombard.  For  what  pur- 
pose was  tobacco  used  by  physicians  before  chloroform  was 
known?  Why  are  athletes  in  training  not  allowed  to  use 
tobacco? 

What  effect  has  tobacco  on  the  nervous  system?  Why  are 
users  of  tobacco  not  good  marksmen  ?  Repeat  what  Luther 
Burbank  said  about  his  workmen.  Give  statistics  showing 
mental  progress  made  in  schools  by  smokers  and  by  non- 
smokers.  What  rule  have  many  great  employers  made  regard- 
ing cigarette  smokers?  How  does  tobacco  affect  the  mind? 
the  digestive  system?  the  arteries?  Discuss  the  effect  upon 
the  body  of  a  moderate  use  of  tobacco. 

SUGGESTIONS  TO  THE  TEACHER 

If  possible,  teach  this  chapter  in  an  informal  manner,  discussing 
local  conditions  when  it  is  possible  to  do  so.  Statistics  as  to  the 
use  of  tobacco  by  the  athletes  and  high  scholarship  students  of  the 
school  may  quickly  be  gathered,  and  the  attitude  of  local  employers 
may  sometimes  be  mentioned.  The  continued  use  of  cigarettes  by 
the  young  can  only  be  ascribed  to  ignorance  concerning  the  results 
of  their  use,  and  the  question  will  form  an  excellent  subject  for  dis- 
cussion at  a  parents'  meeting.  The  Scientific  Temperance  Journal, 


TOBACCO  209 

Boston,  Massachusetts,  prints  much  information  on  this  subject  that 
is  of  value  to  the  teacher.  The  price  of  this  journal  is  60  cents 
a  year. 

Emphasize  again  the  importance  of  forming  correct  habits  and 
how  tobacco  interferes  with  the  formation  of  habits  of  industry.  In 
case  a  good  student  has  recently  begun  the  use  of  tobacco,  call  his 
attention  to  the  fact  that  his  previously  formed  habits  of  study  are 
still  keeping  his  class  standing  high,  but  that  he  should  be  on  the 
alert  for  signs  of  the  drop  in  his  scholarship  record  that  will  in  all 
probability  come  if  the  use  of  tobacco  is  continued.  An  interesting 
side  topic  is  the  early  history  of  the  use  of  tobacco  in  Europe.  The 
securing  of  the  concessions  for  its  sale  by  Sir  Walter  Raleigh  and 
his  efforts  to  extend  its  use  so  that  his  revenues  from  it  might  be 
increased,  have  much  of  human  interest  in  them. 


CHAPTER   TWENTY-ONE 

ALCOHOL 

A  STANDARD  text  on  hygiene  that  was  used  in  many 
of  our  medical  colleges  as  late  as  1890  taught  that 
malaria  was  due  to  miasma  from  swamps ;  that  typhoid 
fever  was  connected  with  the  rise  and  fall  of  ground 
water;  that  cholera  seemed  to  be  related  to  the  tem- 
perature of  the  soil  from  four  to  six  feet  below  the 
surface ;  that  erysipelas  was  due  to  impurities  in  the 
«iir ;  that  diphtheria  was  caused  by  sewer  gas ;  and  that 
yellow  fever  was  an  air-borne  disease. 

These  ideas  seem  strange  to  us  today,  but  the  fact 
that  they  were  current  so  recently  even  among  medical 
men  emphasizes  the  fact  that  in  the  past  men  have 
looked  upon  disease  as  something  that  comes  upon  us 
from  without ;  that  they  have  thought  of  the  causes  of 
sickness  as  lying  in  the  world  about  us.  Now  we  have 
come  to  understand  that  the  causes  of  ill  health  are  to 
be  sought  for,  not  in  the  swamps  and  forests  and  changes 
of  weather,  but  within  the  body  itself ;  that  it  is  what 
goes  into  the  body  rather  than  the  distant  outside  world 
that  is  important  in  hygiene.  We  have  learned  that  the 
great  secret  of  health  is  to  keep  the  lymph  in  which  the 
cells  are  bathed  free  from  poisons  and  impurities  and  to 
allow  the  cells  to  live  their  own  lives  in  a  natural  way. 

Along  with  this  new  knowledge  there  has  come  a 
truer  understanding  of  the  uses  of  medicines  and  a 
greater  care  about  taking  into  the  lymph  strong  drugs 
whose  effects  on  the  delicate  cells  are  not  fully  under- 
stood. The  best  physicians  now  realize  that  all  medi- 
cines are  foreign  and  unnatural  substances  in  the  lymph, 
which  ought  to  be  given  only  when  there  is  good  reason 

210 


ALCOHOL  211 

to  believe  that  the  body  will  be  benefited  by  them;  and 
they  are  continually  amazed  at  the  reckless  and  ignorant 
way  people  pour  patent  medicines  and  other  strong 
drugs  in  upon  their  cells.  In  this  chapter  we  shall 
study  the  effects  on  the  body  of  the  use  of  alcohol,  a 
powerful  drug  that  is  extensively  used  by  the  people  of 
our  country. 

Where  alcohol  comes  from.  Yeast  is  a  small  plant  that 
lives  on  the  skins  of  fruits  and  in  very  rich  earth,  and 
that  often  blows  about  in  the  air.  The  favorite  food  of 
this  small  plant  is  sugar,  and  when  it  falls  into  a  liquid 
that  contains  sugar,  it  grows  and  multiplies  very  rapidly. 
In  doing  this  it  uses  the  sugar  for  food  and  breaks  it  up 
into  water,  carbon  dioxid,  and  alcohol.  This  process  is 
called  fermentation.  The  alcohol  in  all  the  different 
kinds  of  intoxicating  drinks  that  are  used  by  man  comes 
from  the  fermentation  of  sugar  by  yeast. 

Different  kinds  of  alcoholic  drinks.  The  natives  of  the 
tropics  cut  off  the  flower  clusters  of  palm  trees  and  col- 
lect the  juice  that  pours  out  from  the  cut  ends.  This 
contains  much  sugar,  and  after  it  has  been  fermented 
it  contains  great  quantities  of  alcohol.  The  Mexicans 
collect  the  juice  of  the  agave,  or  century  plant,  in  the 
same  way  and  manufacture  an  intoxicating  drink  from 
it.  %  Fruit  juices  are  rich  in  sugar,  and  in  temperate 
countries  the  people  make  wine  by  allowing  them  to 
ferment.  Grapes,  apples,  currants,  and  blackberries 
are  the  fruits  that  are  most  commonly  used  for  this 
purpose.  In  the  manufacture  of  beer,  grain  is  soaked 
in  water  until  it  sprouts,  and  the  starch  in  it  is  digested 
to  sugar  and  dissolved  out  in  water.  Yeast  is  then 
allowed  to  change  the  sugar  in  the  liquid  to  alcohol. 


212  PRIMER   OF  PHYSIOLOGY 

Rum  is  made  by  fermenting  molasses  and  distilling  off 
the  alcohol;  whisky  is  made  by  distilling  the  fer- 
mented liquid  from  sprouting  grains ;  and  brandy  is 
made  by  distilling  fermented  fruit  juice.1  Alcoholic 
drinks  have  different  tastes,  according  to  the  substances 
from  which  they  are  made,  and  some  are  stronger  than 
others,  but  in  all  of  them  it  is  the  alcohol  itself  that 
is  the  important  thing. 

The  use  of  alcohol  injurious  to  the  body.  Is  alcohol 
injurious  to  the  body  ?  In  the  past  there  has  been 
a  division  of  opinion  on  this  point.  Today  we  have 
come  into  an  age  of  science,  and  we  are  substituting 
knowledge  for  guesswork  in  all  fields  of  human  thought. 
What  are  the  facts  in  this  case  ?  Does  taking  alcohol 
among  the  cells  cause  the  body  machine  to  run  a  longer 
or  a  shorter  time,  and  is  it  laid  up  for  repairs  more  days 
or  fewer  days  in  a  year  when  alcohol  is  used  ?  The 
following  statistics  will  give  us  some  information  on  the 
question. 

The  effect  of  alcohol  on  health  and  length  of  life.  In 
Australia  the  workmen  have  benefit  societies  that  pay 
wages  for  time  lost  on  account  of  sickness.  The  records 
of  these  societies  show  that  the  members  of  societies 
that  admit  only  abstainers  lose  but  little  over  half  as 
much  time  on  account  of  illness  as  do  the  members 
of  societies  that  admit  drinkers.  This  indicates  that  the 
use  of  alcohol  increases  sickness.  A  number  of  life  in- 


1  In  distilling  liquors,  the  liquid  (the  fruit  juice  or  the  water  in  which 
the  grain  has  been  soaked)  that  contains  the  fermented  sugar  is  heated, 
and  the  vapor  that  comes  from  it  is  caught  and  condensed.  The  alcohol 
in  the  liquid  is  changed  to  vapor  more  easily  than  water,  and  the  liquors 
that  are  manufactured  in  this  way  are  strong  in  alcohol. 


ALCOHOL  213 

surance  companies  have  kept  records  of  the  deaths  of 
the  abstainers  and  drinkers  among  their  policy  holders 
separately.  When  these  records  are  examined,  the 
results  are  always  the  same,  —  the  death  rate  among  the 
drinkers  is  higher  than  it  is  among  the  abstainers.  The 
following  examples  taken  from  recent  reports  of  insur- 
ance companies  will  illustrate  the  point. 

In  the  ten-year  period  from  September  30,  1900,  to 
September  30,  1910,  the  experience  of  the  Australasian 
Temperance  and  General  Life  Insurance  Society  showed 
that  where  there  were  100  deaths  among  drinkers  there 
were  only  62  deaths  among  abstainers.  The  Manu- 
facturers' Life  Insurance  Company  during  the  nine-year 
period  from  1902  to  1910  inclusive  had  a  death  rate  of 
56  among  abstainers  as  against  100  deaths  among  an 
equal  number  of  drinkers.  For  a  twenty-eight-year 
period,  ending  in  1911,  the  Sceptre  Life  Insurance 
Association  had  67  deaths  among  its  non-drinking  policy 
holders,  where  it  had  100  deaths  among  its  non-abstain- 
ing members.  All  other  records  that  have  been  kept 
show  that  there  are  more  deaths  among  drinkers  than 
among  an  equal  number  of  abstainers  of  the  same  age.1 

1  "There  may  be  some  actuary  in  the  world  who  believes  that  total 
abstainers  do  not  live  as  long  as  non-abstainers,  but  I  never  heard  of  one, 
and  I  have  never  seen  any  figures  showing  an  advantage  in  favor  of 
abstainers  of  less  than  21  per  cent.  Certainly,  adding  one  fifth  to  a  man's 
life  makes  it  worth  while  to  forego  one  class  of  food  or  drink. 

"  Some  years  ago  I  secured  an  opinion  of  an  actuary  on  the  expectation 
of  life  of  a  young  man  of  twenty  who  was  a  total  abstainer  and  of  one  who 
was  a  drinking  man  at  that  age.  The  expectation  of  the  abstainer  was 
42.2  years;  of  the  drinking  man,  15  years."  —  EDWARD  A.  WOODS,  an 
insurance  manager,  quoted  in  Dr.  Henry  Smith  Williams'  Alcohol:  How 
it  affects  the  Individual,  the  Community,  and  the  Race. 


214  PRIMER   OF  PHYSIOLOGY 

We  can  therefore  decide  that  alcohol  used  as  men  ordi- 
narily use  it  causes  sickness  and  shortens  life  ;  and  since 
this  is  true,  it  must  also  be  true  that  it  is  injurious  to  the 
cells. 

The  effects  of  alcohol  on  the  structure  of  the  cells. 
Alcohol  causes  fatty  degeneration  and  fibroid  degenera- 
tion of  certain  of  the  tissues.1  In  fatty  degeneration 
little  droplets  of  oil  begin  to  collect  within  the  cell,  and 
gradually  the  living  protoplasm  of  the  cell  is  replaced 
by  fat,  until  sometimes  the  cells  become  mere  bags  of  oil. 
When  the  cells  of  the  gastric  glands  are  changed  in  this 
way,  they  lose  their  power  to  secrete ;  when  the  muscle 
cells  of  the  heart  are  changed  to  fat,  they  lose  their 
strength ;  when  the  walls  of  the  arteries  are  affected, 
they  are,  of  course,  weakened ;  and  when  there  is  fatty 
degeneration  of  the  liver,  kidneys,  or  nerve  fibers,  we 
must  expect  these  organs  to  fail  in  their  work. 

The  tissues  most  commonly  affected  by  fibroid  degen- 
eration are  those  of  the  liver,  kidneys,  arteries,  heart, 
and  brain.  In  this  kind  of  degeneration  there  is  an 
overgrowth  of  the  connective  tissue  elements,  while  the 
working  cells  degenerate  and  die.  *  Often  in  the  arteries 
the  elastic  muscle  coat  is  not  only  changed  to  connective 
tissue,  but  lime  is  deposited  in  the  walls.  These  changes 
make  "  pipe-stem  "  arteries,  which  are  brittle  and  often 
have  the  opening  in  them  narrowed  until  it  is  with  great 
difficulty  that  the  blood  makes  its  way  through  them. 

1  As  we  have  already  explained  (page  155),  there  is  good  reason  to 
believe  that  in  some  of  these  changes  in  the  tissues  it  is  intestinal  toxins 
rather  than  the  alcohol  that  really  causes  the  trouble,  but  since  it  is  the 
drinking  of  the  alcohol  that  causes  the  toxins  to  be  formed,  the  fault  in  the 
end  goes  back  to  the  alcohol. 


ALCOHOL  21$ 

Some  diseases  that  may  be  caused  by  alcohol.     In  the 

United  States  each  year  there  are  about  4,000  deaths 
that  are  directly  due  to  the  use  of  alcohol.  Certain 
diseases,  moreover,  are  more  common  among  drinkers 
than  among  abstainers,  and  it  is  believed  that  much  sick- 
ness and  many  deaths  are  due  to  accidents  and  diseases 
that  are  brought  on  by  the  use  of  alcoholic  drinks. 

Prominent  among  the  causes  of  death  that  are  con- 
nected with  the  use  of  alcohol  are :  hardening  of  the 
liver,  in  which  the  liver  turns  to  connective  tissue  and 
shrinks  into  a  small,  hard  organ  utterly  incapable  of 
doing  the  work  which  it  is  supposed  to  do ;  diseases  of 
the  kidneys,  in  which  these  organs  degenerate  and  fail 
in  their  work  of  excreting  the  poisonous  wastes ;  heart 
disease,  which  may  take  many  forms ;  hardening  of  the 
arteries ;  apoplexy  and  paralysis,  which  are  due  to  the 
bursting  of  blood  vessels  in  the  brain ;  insanity  and 
other  diseases  of  the  nervous  system ;  tuberculosis,  pneu- 
monia, and  other  germ  diseases,  to  which  the  user  of 
alcohol  falls  a  victim  because  he  has  weakened  the 
defenses  of  his  body ;  and  accidents  that  would  never 
have  occurred  had  not  some  one  been  under  the  influ- 
ence of  drink. 

It  will  be  noticed  that  the  chief  effects  of  alcohol, 
aside  from  those  on  the  nervous  system,  are  on  the  heart, 
blood  vessels,  lungs,  stomach,  liver,  and  kidneys,  —  the 
great  internal  organs  that  supply  the  body  with  food 
and  oxygen  and  dispose  of  its  wastes.  When  we  re- 
member how  the  life  of  the  whole  body  requires  that 
the  work  of  these  organs  be  efficiently  performed,  it  is 
easy  for  us  to  understand  that  anything  that  injures 
them  is  of  first  importance  in  the  realm  of  health. 


2l6  PRIMER   OF  PHYSIOLOGY 

The  effects  of  a  continued  moderate  use  of  alcohol 
It  should  be  understood  that,  except  for  certain  effects 
on  the  brain,  we  are  discussing  in  this  chapter  the 
effects  of  what  is  called  moderate  drinking  on  the  body ; 
for  when  alcohol  is  used  day  after  day,  even  though  it 
be  used  very  moderately,  there  is  a  piling  up  of  its 
effects  on  the  tissues.  Indeed,  the  cells  of  the  man 
who  drinks  a  moderate  amount  of  beer  or  wine  daily 
are  never  free  from  the  influence  of  alcohol.  Beer 
drinkers  suffer  most  of  all  from  fatty  degeneration  of 
the  tissues,  and  one  need  never  become  intoxicated  to 
experience  the  evil  effects  from  alcohol  that  have  been 
described  above.1  The  shortening  of  life  given  on 
page  2 1 3  is  in  moderate  drinkers  and  not  in  drunkards ; 
for  the  death-rate  among  those  who  habitually  drink 
to  intoxication  is  so  high  that  no  insurance  company 
will  accept  them.2 

The  effects  of  alcohol  on  the  mind.  Because  alcohol 
causes  a  person  to  seem  lively  and  to  talk  more  easily, 
it  is  commonly  believed  that  it  is  a  stimulant.  This  is  a 
mistake.  Alcohol  is  a  narcotic,  and  it  produces  its 
seemingly  stimulating  effect  by  paralyzing  the  higher 

1  "  Alcoholic  diseases  are  certainly  not  limited  to  persons  recognized  as 
drunkards.      Instances   have   been   recorded   in   increasing   numbers   in 
iccent' years  of  the  occurrences  of  diseases  of  the  circulatory,  renal,  and 
nervous  systems,  reasonably  or  positively  attributable  to  the  use  of  alco- 
holic liquors  in  persons  who  never  became  really  intoxicated  and  were 
regarded  by  themselves  and  others  as '  moderate  drinkers.' " 

—  DR.  WILLIAM  WELCH. 

2  A  few  of  those  classed  as  drinkers  may  have  become  heavy  drinkers 
after  they  were  insured,  but  insurance  companies  reject  not  only  drunkards, 
but  also  those  who  seem  likely  to  become  drunkards.     The  comparison  is, 
therefore,  in  the  main  between  abstainers  and  moderate  drinkers. 


ALCOHOL  217 

centers  of  the  brain  and  allowing  the  person  to  do  and 
say  things  that,  ordinarily  his  good  sense  keeps  him 
from  doing  and  saying.  In  one  set  of  experiments  it 
was  found  that  20  to  40  grams  of  alcohol  (the  amount  in 
from  one  to  two  quarts  of  beer)  taken  on  twelve  suc- 
cessive days  lessened  the  capacity  to  add  numbers  40 
per  cent  and  the  ability  to  memorize  poetry  70  per  cent. 

Other  experiments  show  that  the  capacity  to  think 
clearly  and  to  judge  correctly  is  greatly  influenced  by 
even  small  quantities  of  alcohol.  Typesetters  who  were 
given  only  a  little  over  an  ounce  of  alcohol  a  day  did 
10  per  cent  less  work  and  made  25  per  cent  more  mis- 
takes than  on  days  when  no  alcohol  was  taken,  and  the 
effect  of  these  small  doses  of  alcohol  continued  48  hours. 

After  taking  a  drink,  a  man  feels  that  his  mind  is 
working  better  and  that  his  ideas  come  more  easily  and 
freely.  The  truth  is  that  his  mind  is  slower  and  his 
ideas  are  less  sensible  than  usual,  but  the  powers  of  his 
mind  by  which  he  judges  of  these  things  have  been 
deadened  by  the  alcohol,  and  he  is  no  longer  capable 
of  forming  a  correct  opinion  of  his  own  acts. 

The  effect  of  alcohol  on  the  strength  and  control  of  the 
muscles.  The  man  who  has  taken  alcohol  always  feels 
that  he  is  stronger  and  has  more  endurance  because  of 
it.  In  this  case,  again,  the  alcohol  user  is  mistaken  as 
to  his  real  condition,  as  facts  like  the  following  prove : 

About  sixteen  years  ago,  Professor  Durig,  a  chemist 
and  an  expert  mountain  climber,  carried  on  a  series 
of  experiments  by  repeatedly  climbing  a  peak  in  the 
Alps.  On  certain  days  he  drank  alcohol  equal  to  the 
amount  in  two  glasses  of  beer ;  on  other  days  no  al- 
cohol was  taken.  He  was  accustomed  to  use  moderate 


2l8  PRIMER   OF  PHYSIOLOGY 

amounts  of  alcohol,  and  he  felt  that  he  worked  more 
easily  on  alcohol  days,  but  to  his  surprise  he  found  that 
on  those  days  he  expended  15  per  cent  more  energy 
and  required  more  than  one  fifth  longer  to  climb  the 
mountain.  Other  tests  carried  on  for  ten  days  in  the 
laboratory  showed  that  two  glasses  of  beer  taken  at 
dinner  reduced  the  working  power  of  the  muscles  10 
per  cent.  "  Alcohol  gives,  not  strength,  but  only  a 
feeling  of  strength,  to  the  muscles."  It  deadens  the 
ability  to  feel  fatigue,  but  does  not  relieve  fatigue. 

It  is  probable  that  the  weakening  effect  of  alcohol  on 
the  muscles  is  mainly  due  to  its  interference  with  their 
control  by  the  nervous  system.  The  movements  are 
made  awkwardly,  and  the  muscles  work  against  each 
other,  and  so  much  of  their  power  is  lost.  This  lack  of 
fineness  of  control  in  alcohol  users  is  shown  at  once 
in  a  baseball  pitcher,  a  bowler,  a  rifleman,  or  any 
one  who  does  work  that  requires  each  muscle  to  work 
exactly  the  right  amount  and  at  exactly  the  right 
moment. 

Why  alcoholic  drinks  have  been  banished  from  the 
United  States.  When  the  Great  War  came  and  nations 
were  put  to  the  test,  practically  all  those  that  were 
called  on  to  put  forth  all  their  effort  restricted  the 
manufacture  and  sale  of  alcoholic  drinks.  No  argu- 
ment was  needed  to  convince  the  peoples  that  the  manu- 
facture of  intoxicating  drinks  was  a  waste  of  foodstuffs 
and  their  use  a  hindrance  in  the  prosecution  of  the  war ; 
deep  within  their  consciousness  they  knew  that  alcohol 
was  an  evil.  They  were  shaking  off  everything  that 
would  hinder  them  in  the  great  fight  and  they  knew 
that  the  use  of  intoxicating  drinks  would  sap  the 


ALCOHOL  219 

strength  and  becloud  the  minds  of  those  who  needed 
clear  intellects  and  strong  bodies  for  the  struggle. 

Now  that  the  war  is  over  the  people  of  our  own 
country  have  decided  that  intoxicating  drinks  shall  be 
sold  in  it  no  more.  Some  of  the  reasons  that  moved 
them  to  this  decision  have  been  set  forth  in  this  chapter. 
The  majority  of  them  were  convinced  that  alcohol  is 
injurious  to  health,  morals,  and  efficiency,  and  they 
saw  no  reason  why  in  times  of  peace  any  more  than  in 
times  of  war  an  unnecessary  burden  should  be  imposed 
on  our  land.  After  seventy-five  years  of  discussion  of 
the  question  our  people,  through  their  representatives, 
have  declared  that  the  time  when  intoxicating  drinks 
can  be  sold  in  the  United  States  has  passed.  This  de- 
cision is  doubtless  wise;  the  combined  judgment  of  an 
intelligent  people  on  any  question  with  which  they  have 
long  been  familiar  is  usually  correct.  Once  again 
America  has  led  the  way,  and  in  time  the  other  great 
nations  of  the  earth  will  doubtless  follow  the  example 
she  has  set. 

QUESTIONS 

How  is  alcohol  produced  ?  How  is  alcohol  made  in  the 
tropics  ?  How  is  wine  made  ?  How  is  beer  made  ?  Name 
some  distilled  liquors. 

What  effect  has  the  use  of  alcohol  on  the-health  ?  Give 
statistics  showing  its  effect  on  the  death-rate. 

Explain  what  is  meant  by  fatty  degeneration.  What  organs 
may  be  affected  in  this  way  ?  What  changes  take  place  in 
fibroid  degeneration  ?  What  organs  are  commonly  affected 
in  this  way  ?  Explain  the  result  of  fibroid  degeneration  of  the 
arteries. 

In  the  United  States  how  many  deaths  each  year  are  due  to 


220  PRIMER   OF  PHYSIOLOGY 

alcohol  ?  How  many  are  directly  caused  by  alcohol  ?  Name 
some  diseases  that  are  often  caused  by  the  use  of  alcohol. 
What  organs  of  the  body  are  most  affected  by  the  use  of 
alcohol  ?  What  effects  has  moderate  drinking  on  the  body  ? 

Why  is  it  commonly  believed  that  alcohol  stimulates  the 
mind  ?  What  effect  have  small  amounts  of  alcohol  on  the 
power  to  add  numbers  ?  to  memorize  ?  Describe  the  experi- 
ment in  which  typesetters  were  given  small  amounts  of 
alcohol. 

Explain  the  effects  of  alcohol  on  the  muscles. 

SUGGESTIONS   TO   THE  TEACHER 

In  teaching  this  chapter,  nothing  is  so  important  as  to  get  the 
facts  before  the  pupils.  The  two  most  easily  accessible  sources 
of  facts  in  regard  to  the  effects  of  alcohol  are  Dr.  Henry  Smith 
Williams'  Alcohol:  How  it  Affects  the  Individual,  the  Community, 
and  the  Race  (The  Century  Company,  New  York)  and  the  numbers 
of  the  Scientific  Temperance  Journal  (see  page  208).  This  journal 
gives,  through  summaries  and  abstracts,  the  results  of  scientific  ex- 
periments in  this  field  and  translates  articles  dealing  with  the  very 
important  work  that  is  now  being  carried  on  in  different  European 
countries 


CHAPTER   TWENTY-TWO 


ACCIDENTS 

"  IN  time  of  peace  prepare  for  war."  In  every  house 
there  should  be  kept  in  a  small  box  or  drawer  certain 
articles  for  use  in  case  of  accident.  Among  these  arti- 
cles should  be  soft,  worn-out  towels ;  cotton  or  linen  cloths 
three  to  six  inches  square; 
rolls  of  bandages  varying  from 
one  half  inch  to  three  inches 
in  width  and  from  one  to  two 
yards  in  length ;  a  bar  of  green 
soap  ;  threaded  needles,  scis- 
sors, and  safety  pins  ;  borated 
vaselin  ;  bichlorid  or  biniodid 
of  mercury  disks ;  powdered 
boracic  acid ;  and  a  bottle  of 
collodion.  Accidents  come 
without  warning,  and  having 
these  supplies  ready  may  save 
suffering  or  even  life. 

Bandages.  Since  many  small  hurts  are  treated  with- 
out the  aid  of  a  physician,  it  is  well  to  understand  how 
to  put  on  a  bandage  neatly,  comfortably,  and  securely. 
When  the  part  that  is  to  be  bandaged  is  of  nearly  the 
same  circumference  throughout,  the  bandage  should 
simply  be  rolled  around  the  part  from  below  upward, 
each  turn  of  the  cloth  covering  two  thirds  of  the  one 
below.  When  the  part  that  is  to  be.bandaged  is  thicker 
in  one  part  than  in  another,  as  the  forearm  or  leg,  the 
bandage  may  be  made  to  lie  smooth  and  flat  by  revers- 
ing each  turn  after  the  first  few  turns.  To  reverse  a 
bandage,  hold  it  at  its  lower  edge  and  turn  it  one  half 

221 


FlGS.  138  and  139.  Showing  a 
circular  bandage  and  the  method  of 
reversing  a  bandage. 


222 


PRIMER   OF  PHYSIOLOGY 


over  towards  you.  To  give  a  neat  appearance,  make 
each  reverse  directly  above  the  one  preceding  it.  The 
figure-of-eight  bandage  is  useful 
about  joints.  The  best  way  to 
get  an  understanding  of  the  dif- 
ferent bandages  here  described  is 
to  study  the  illustrations  in  Fig- 
ures 138  to  143.  After  two  turns 
have  been  put  on,  the  bandage 
should  be  firmly  stitched,  and, 
after  the  bandage  is  completed, 
the  end  should  be  securely  sewed. 
A  row  of  stitches  from  top  to 
bottom,  one  in  each  turn  of  the 
bandage,  is  of  great  advantage 
in  preventing  slipping.  Always 
bandage  firmly,  but  never  too 
tightly,  and  use  an  equal  pressure 
throughout  the  bandage. 

Wounds.  It  is  well  that  a  cut 
should  bleed  freely,  as  the  blood 
assists  in  washing  out  and  killing 
any  germs  that  may  be  in  the 
wound.  If  the  cut  has  been  made 
with  a  clean  instrument,  it  may  be 
FIGS. '140, 141, 142,  and  143.  bandaged  without  any  treatment 
A  reversed  bandage  and  a  t  n  bandaged  after  being 

figure-of-eight  bandage  on  tlje 

hand;  a  figure-of-eight  band-  dusted      with      powdered      boracic 

age  and  a  reversed  bandage  ^          A    wound     made     by     an 

on  the  foot.  J 

unclean    instrument    should    be 

washed  with  soap  and  water  and  treated  with  powdered 
boracic  acid  or  borated  vaselin.     If  the  person  must  use 


ACCIDENTS 


223 


the  injured  part  in  attending  to  his  work,  two  bandages 
should  be  put  on.  The  outer  one  may  be  changed  when 
it  is  soiled,  but  unless  the  wound  becomes  red  and  pain- 
ful and  has  matter  in  it,  the  inner  bandage  should  be  left 
undisturbed  until  the  injury  has  healed. 

Deep  wounds,  such  as  are  made  by  rusty  nails  that 
have  become  soiled  by  lying  about  barnyards,  are  dan- 
gerous, because  frequently  tetanus  germs  get  into  them. 
A  puncture  or  other  wound  that  is  so  deep  that  it  can- 
not be  thoroughly  cleansed  ought  to  be  treated  by  a 
physician,  who  will  know  whether  it  is  advisable  to  use 
tetanus  antitoxin  as  a  safeguard  against  danger  from 
tetanus  germs. 

Bleeding.  When  blood  flows  in  jets  and  has  a  bright 
red  color,  an  artery  has  been  cut.  If  the  blood  flows  in 
a  steady  stream,  it  is  a  vein  that 
has  been  severed.  In  either 
case,  a  physician  should  be 
called  at  once.  In  the  mean- 
time, control  the  bleeding  by 
pressing  on  the  vessel  with  the 
thumbs.  The  pressure  should 
be  applied  between  the  wound 
and  the  heart  if  the  cut  vessel 
is  an  artery ;  beyond  the  wound, 
if  the  bleeding  is  from  a  vein. 
If  the  physician  is  long  in 
coming,  or  if  the  bleeding  can- 
not be  controlled  by  pressure  with  the  thumbs,  twist 
a  handkerchief  about  the  limb,  as  shown  in  Figure  144. 
The  blood  should  not  be  shut  off  from  the  limb  for 
longer  than  an  hour,  as  much  damage  may  be  done  by 


FIG.  144.    Checking  bleeding 
from  a  wound. 


224  PRIMER   OF  PHYSIOLOGY 

depriving  the  cells  of  their  supply  of  blood  for  too  long 
a  time. 

Blows  on  the  head.  A  blow  on  the  head  sometimes 
ruptures  a  blood  vessel  within  the  cranium  and  causes 
a  blood  clot  to  form  on  the  brain.  If,  a  person  becomes 
sleepy  after  such  a  blow,  a  physician  should  be  called  at 
once.  It  is  well  to  wake  the  person  occasionally  during 
the  night  after  such  an  injury;  for  otherwise  he  may 
sink  into  unconsciousness  without  its  being  discovered. 

Burning  clothing.  If  your  clothing  should  take  fire, 
do  not  start  to  run.  If  possible,  remove  the  burning 
garment  at  once.  If  this  cannot  be  done,  remember  that 
a  fire  cannot  burn  without  air,  and  that  the  quickest  way 
to  put  out  burning  clothing  is  to  lie  down  and  wrap  your- 
self in  a  blanket  or  rug,  or  in  anything  else  that  you  can 
lay  hands  on.  If  nothing  is  at  hand  that  can  be  used  as 
a  covering  to  smother  the  fire,  lie  down  and  roll  over  and 
over.  In  any  case,  lie  down  so  that  the  flames  will  not 
come  up  about  your  face ;  for  inhaling  a  flame  is  often 
followed  by  very  serious  consequences.  In  passing  close 
to  a  fire,  as  in  a  burning  building,  the  face  should  be  pro- 
tected if  possible  by  something  held  before  it. 

The  treatment  of  burns.  A  burn  in  which  the  skin  is 
only  reddened,  or  in  which  the  blistering  is  slight,  may 
be  treated  by  simply  shutting  the  air  away  from  it. 
A  paste  made  of  baking  soda  and  water,  or  of  flour  or 
starch  mixed  with  water,  is  good  for  this  purpose. 
White  of  egg,  vaselin,  olive  oil,  castor  oil,  fresh  lard,  or 
cream  may  also  be  used  to  cover  a  burn.  Wet  cloths 
wrung  out  of  cold  water  will  help  to  allay  the  pain. 
Burns  which  cover  much  surface,  or  small,  deep  burns, 
should  be  shown  to  a  physician;  for  it  is  not  always 


ACCIDENTS 


22$ 


possible  to  tell  at  first  how  much  damage  has  been  done, 
and  the  injury  may  be  more  severe  than  it  appears 
to  be. 

A  burn  made  by  an  acid  should  be  washed  and 
treated  with  limewater,  baking  soda,  or  soapsuds.  A 
burn  made  by  an  alkali  (such  as  lime,  lye,  etc.)  may  be 
treated,  after  thoroughly  washing  off  the  alkali,  with 
weak  vinegar,  lemon  juice,  sour  milk,  or  buttermilk. 

Apparent  drowning.  Drain  the  water  from  the  pa- 
tient's lungs  by  catching  him  under  the  waist  and  hold- 
ing him  for  a  few 
seconds  with  the  head 
hanging  down.  Then 
quickly  lay  him  in 
the  position  shown 
in  Figure  145,  with  a 
folded  coat  or  blanket 
under  his  chest. 
Place  the  hands  on 

either  Side  Of  the  back    FlG"  I4S'    Carrying  on  artificial  respiration. 

over  the  lower  ribs.  Throw  the  weight  of  the  body  steadily 
downward  on  the  hands  and  drive  the  air  out  of  the  lungs. 
Take  the  pressure  off  the  body  without  lifting  the  hands, 
and  allow  the  air  to  come  into  the  lungs.  Repeat  about 
fifteen  times  a  minute.  This  method  sends  more  air 
through  the  lungs  than  any  of  the  methods  in  which 
the  patient  is  laid  on  his  back,  and  it  has  the  additional 
advantage  that  the  tongue  does  not  fall  back  and  block 
the  throat. 

Rubbing  the  limbs  along  the  veins  toward  the  heart 
causes  the  blood  to  circulate  and  should  be  kept  up  if 
there  is  a  second  person  to  attend  to  it.  Keep  the 


226  PRIMER   OF  PHYSIOLOGY 

patient  as  warm  as  possible  by  covering  him  with  a 
blanket  and  pouring  warm  water  over  him,  or  by  laying 
hot-water  bottles  about  him.  A  hot-water  bottle  at  the 
head  is  especially  important,  but  nothing  hotter  than 
can  be  borne  comfortably  by  the  skin  of  the  elbow 
should  be  brought  into  contact  with  an  unconscious  per- 
son. When  the  patient  begins  to  revive,  give  strong  hot 
coffee,  or  fifteen  drops  of  ammonia  in  a  glass  of  water. 
Artificial  respiration  should  be  kept  up  for  an  hour  or 
longer  if  the  person  does  not  recover  sooner. 

Suffocation.  Suffocation  may  be  produced  by  hanging, 
by  choking,  or  by  gas  or  smoke  poisoning.  Sprinkle 
cold  water  on  the  face;  carry  on  artificial  respiration 
as  in  cases  of  apparent  drowning ;  and,  when  the  person 
is  able  to  swallow,  give  stimulants  as  directed  above. 

Fainting.  Lay  the  patient  flat  on  his  back,  so  that 
the  blood  will  flow  easily  to  the  head.  Sprinkle  cold 
water  on  the  face,  and  give  him  fresh  air.  Give  strong 
coffee  or  ammonia  as  directed  above. 

Dangers  from  electricity.  As  the  use  of  electricity 
becomes  more  common,  it  is  more  and  more  frequently 
a  source  of  accidents.  Even  now  many  people  do  not 
seem  to  know  that  highly  charged  electric  wires  and 
third  rails  are  deadly  affairs,  and  that  those  who  do  not 
understand  their  workings  ought  not  to  take  chances 
with,  them.  Where  a  notice  is  posted  warning  the 
public  not  to  cross  the  track  of  an  electric  line,  there  is 
a  reason  for  the  warning,  and  you  should  keep  off  the 
track.  When  a  trolley  wire  or  an  electric  wire  breaks 
and  faMs  to  the  ground,  keep  away  from  it.  It  is  in- 
teresting to  experiment  with  electricity,  but  you  cannot 
afford  to  begin  in  this  way. 


ACCIDENTS  227 

Rescuing  a  person  from  an  electric  wire  or  a  third  rail. 

A  live  wire  lying  on  a  person  may  be  safely  flipped  off 
with  a  dry  board  or  stick.  If  the  person  is  lying  on 
the  wire,  the  wire  may  safely  be  cut  with  an  ax  or 
hatchet  that  has  a  dry  wooden  handle.  Cut  between 
the  person  and  the  source  of  the  electricity ;  on  both 
sides,  if  the  source  of  the  electricity  is  unknown. 

In  trying  to  pull  a  person  off  a  live  wire  or  third  rail, 
great  care  is  necessary  or  the  rescuer  will  be  injured. 
In  attempting  to  do  this,  unless  the  ground  is  very  dry, 
one  should  stand  on  a  dry  board,  a  folded  coat,  or 
several  thicknesses  of  folded  newspapers.  A  rubber 
mat  is  better  than  the  articles  just  mentioned,  but  it  is 
not  often  at  hand.  If  possible,  take  hold  of  the  per- 
son through  dry  cloth  or  paper,  and  catch  him  by  the 
clothing  without  allowing  the  hand  to  come  into  contact 
with  his  body.  Pull  him  off  the  rail  or  wire  with  one 
quick,  firm  motion,  and  if  he  is  not  breathing,  carry  on 
artificial  respiration  as  in  cases  of  apparent  drowning. 
A  doctor  should  be  sent  for  as  quickly  as  possible. 

Foreign  bodies  in  the  eye.  If  a  cinder  or  other  foreign 
body  gets  into  the  eye,  do  not  rub  the  eye.  Keep  it 
closed  and  the  tears  will  often  wash  the  dirt  out  into 
view  so  that  it  may  easily  be  removed.  Sometimes 
stretching  the  upper  lid  down  over  the  lower  lid  two  or 
three  times,  or  closing  the  nostril  on  the  opposite  side 
and  blowing  the  nose  hard,  will  change  the  position  of 
the  object  and  make  it  possible  to  remove  it.  The  inner 
surface  of  the  lower  lid  may  be  examined  by  pressing 
the  lid  down,  and  some  persons  are  skillful  enough  to 
turn  the  upper  lid  back  over  a  match  or  small  stick  so 
that  the  offending  particle  can  be  wiped  off.  Only 


228  PRIMER   OF  PHYSIOLOGY 

clean  fingers,  clean  handkerchiefs,  or  other  clean  objects 
should  be  allowed  to  touch  the  eye.  After  the  foreign 
body  has  been  removed,  a  few  drops  of  boracic  acid 
solution  is  soothing  and  is  useful  in  safeguarding  against 
possible  infection  with  germs. 

Foreign  bodies  in  the  nose  and  throat.  Little  children 
sometimes  push  beans,  peas,  beads,  or  other  objects  into 
their  noses.  Having  the  child  blow  the  nose  will  often 
bring  these  objects  out,  but  if  they  cannot  be  removed 
in  this  way  a  physician  should  be  called.  Do  not  try 
to  remove  them  with  a  hairpin  or  other  sharp  instru- 
ment. 

When  a  button,  coin,  or  other  object  sticks  in  the 
throat,  the  child  should  be  seized  by  the  feet,  suspended 
head  downward,  and  energetically  shaken  and  slapped 
on  the  back.  Usually  this  will  cause  the  object  in  the 
throat  to  drop  out. 

Treatment  for  swallowed  pins  and  needles.  When  a 
pin  or  needle  has  been  swallowed,  a  large  meal  of  bread, 
potatoes,  cabbage,  or  other  coarse  foods  shpuld  be  eaten, 
as  they  will  leave  a  large  amount  of  undigested  matter 
to  coat  the  foreign  object  during  its  passage  through 
the  alimentary  canal.  Never  give  a  laxative  under  suck 
conditions.  No  anxiety  need  be  felt  over  swallowed  but- 
tons, coins,  and  other  similar  objects. 

Frostbite.  Keep  away  from  the  fire  and  thaw  the 
"bitten"  part  out  very  gradually  by  rubbing  it  with 
snow,  or  by  keeping  it  bathed  in  ice  water  until  the 
blood  begins  to  circulate  through  it  again.  Suddenly 
thawing  the  frozen  tissues  is  far  more  injurious  than  the 
freezing,  and  every  care  should  be  taken  to  keep  in  a 
cool  atmosphere  until  the  thawing  process  is  completed. 


ACCIDENTS  229 

Ivy  poisoning.  Dissolve  a  level  teaspoonful  of  potas- 
sium permanganate  crystals  in  a  pint  of  water  and 
bathe  the  affected  parts.  Before  the  skin  is  broken 


FIGS.  146  and  147.  The  poison  ivy  is  often  mistaken  for  the  Virginia  creeper. 
The  Virginia  creeper  has  five  leaves,  while  the  poison  ivy  has  only  three. 

the  poisgnous  oil  may  be  partially  removed  at  least  by 
thorough  washing  with  strong  soap  or  with  alcohol.  In 
severe  cases  a  physician  should  be  consulted. 

Poisoning.  Bottles  that  contain  poisons  should  not  be 
kept  among  medicines,  and  it  is  well  to  paste  strips  of 
sandpaper  on  such  bottles,  so  that  they  can  be  recog- 
nized even  in  the  dark.  When  a  poison  is  taken  by 
accident,  a  physician  should  be  called  immediately.  If 
possible,  have  the  messenger  tell  him  what  poison  has 
been  taken,  so  that  the  proper  antidote  may  be  brought. 

A  card  with  a  list  of  the  different  poisons  and  their 
antidotes  should  be  written  out,  and  placed  with  the 
other  articles  that  are  kept  for  use  in  case  of  accident. 
The  sooner  the  antidote  is  given,  the  less  time  will  the 
poison  have  to  damage  the  body,  and  when  one  is  thus 
prepared,  a  case  of  poisoning  can  often  be  treated  be- 
fore the  doctor  arrives. 


230  PRIMER   OF  PHYSIOLOGY 

While  waiting  for  the  doctor,  give  an  emetic  at  once 
to  produce  profuse  vomiting,  if  the  poison  is  not  an 
acid.  Good  emetics  are  :  mustard  and  water ;  salt  and 
water ;  lukewarm  water  alone  and  in  large  quantities ; 
and  ipecac.  Tickling  the  throat  with  a  feather  or  thrust- 
ing the  finger  into  the  throat  will  help  to  cause  vomiting. 

The  following  list  of  antidotes  for  some  of  the  more 
common  poisons  may  be  found  useful : 

Acids.  Give  soda,  chalk,  old  mortar,  or  soap.  Oil 
and  milk  are  useful.  For  carbolic  acid  use  alcohol 
(whisky  or  brandy  will  do).  Oil  or  milk  should  be  used 
if  no  alcohol  is  at  hand. 

Arsenic.  This  is  the  poison  in  Fowler's  Solution, 
Paris  Green,  and  Rough  on  Rats.  Give  any  medicine 
that  contains  iron. 

Mercuric  chlorid.  This  is  also  called  bichlorid  of 
mercury  and  corrosive  sublimate.  Give  milk,  white  of 
egg,  or  both.  Flour  or  starch  with  milk  and  egg  is  good. 

Phosphorus.  Magnesia  and  chalk  in  water,  and  white 
of  egg  are  good  remedies.  Do  not  give  oil  or  milk. 
Phosphorus  is  the  poisonous  substance  on  the  end  of 
matches,  and  is  often  found  in  rat  poison. 

Opium,  laudanum,  nightshade,  and  jimson  weed.  Give 
strong  coffee  or  ammonia.  Keep  the  patient  awake  by 
walking  him  about,  slapping  him,  or  throwing  cold 
water  over  him,  if  necessary.  Give  stimulants  as  di- 
rected under  Fainting,  on  page  226. 

Strychnin.  Inhaling  chloroform  or  ether  will  quiet 
the  patient.  Give  five  grains  of  sodium  bromid  every 
half  hour.  Keep  the  patient  away  from  cold  drafts  and 
noises,  and  allow  nothing  to  touch  him,  as  any  stimulus 
makes  the  spasms  more  violent. 


ACCIDENTS  231 

Preventing  accidents.  The  first  step  in  preventing 
accidents  is  so  to  arrange  the  conditions  under  which 
we  live  and  work  that  it  will  be  difficult  for  mishaps  to 
occur.  In  machine  shops  and  factories  and  on  railroads, 
this  is  rapidly  being  done.  The  causes  of  accidents  in 
private  homes  and  on  farms  should  also  be  removed ; 
for  many  houses  are  built  with  dangerously  steep  cellar 
stairs ;  many  barn  lofts  can  be  entered  only  by  climbing 
rickety  ladders;  stairways  and  openings  in  floors  that 
are  left  unprotected  by  railings  are  the  cause  of  many 
falls ;  and  farm  machinery  is  constantly  being  operated 
in  a  dangerous  and  careless  way.  All  these  and  other 
conditions  that  cause  accidents  should  be  remedied,  and 
when  this  is  done  the  number  of  accidents  is  at  once 
greatly  reduced. 

The  other  important  factor  in  the  prevention  of  acci- 
dents is  the  use  of  intelligence  and  reasonable  care 
when  it  is  possible  for  carelessness  to  cause  an  accident 
to  happen.  In  our  cities  children  are  continually  run- 
ning directly  in  the  way  of  automobiles  and  street  cars ; 
drownings  occur  because  of  a  lack  of  care  in  handling 
boats  and  because  persons  who  cannot  swim  venture 
into  water  beyond  their  depth  ;  clothing  is  set  ablate  by 
standing  too  near  an  open  fire ;  and  automobile  acci- 
dents occur  because  of  recklessness  in  driving  these 
machines.  Accidents  of  this  kind  can  only  be  pre- 
vented by  intelligence  and  watchfulness,  and  you  should 
constantly  educate  yourself  in  those  habits  that  prevent 
them. 

More  people  are  injured  by  falling  than  in  any  other 
way,  and  the  most  common  cause  of  falls  is  carelessly 
placed  ladders.  An  ordinary  ladder  should  not  be  set 


232  PRIMER    OF  PHYSIOLOGY 

too  straight  or  too  slanting,  and  a  three-legged  stepladder 
stands  more  securely  than  a  four-legged  one. 

The  problem  of  accidents  is  more  important  than  is 
generally  understood  (Fig.  148),  as  in  addition  to  the 
killed,  hundreds  of  thousands  of  persons  are  injured  in 
them  each  year. 

QUESTIONS 

Name  some  articles  that  should  be  kept  for  use  in  case  of 
accident.  Name  three  kinds  of  bandages  and  tell  how  each  is 
put  on.  Describe  the  treatment  for  cuts.  Why  is  a  deep 
wound  made  by  an  unclean  instrument  dangerous  ?  When 
blood  is  flowing  from  a  wound,  how  can  you  tell  whether  it 
comes  from  a  vein  or  an  artery  ?  How  can  the  bleeding  be 
checked  until  a  physician  arrives? 

Why  should  a  person  not  be  allowed  to  sleep  uninterruptedly 
after  a  blow  on  the  head  ?  If  your  clothing  were  to  catch  fire, 
what  should  you  do  ?  Describe  the  treatment  of  burns.  De- 
scribe artificial  respiration.  When  should  it  be  used  ?  In 
addition  to  carrying  on  artificial  respiration,  what  else  may  be 
done  in  cases  of  apparent  drowning?  What  should  be  done 
in  cases  of  suffocation  ?  What  should  be  done  for  a  person 
who  has  fainted  ? 

Tell  how  a  person  may  be  rescued  from  a  live  wire  or  a 
third  rail.  How  may  foreign  bodies  be  removed  from  the  eye  ? 
from  the  nose  ?  from  the  throat  ?  What  is  the  treatment  for 
swallowed  pins  and  needles  ?  for  frostbite  ?  for  ivy  poisoning  ? 
Give  antidotes  for  the  following  poisons :  carbolic  acid ; 
arsenic  ;  mercuric  chlorid  ;  phosphorus.  Give  the  treatment 
for  a  case  of  strychnin  poison.  In  what  two  ways  can 
accidents  be  prevented. 


CHAPTER   TWENTY-THREE 

REALIZING  HEALTH  POSSIBILITIES 

WHEN  a  farmer  begins  to  study  how  to  increase  his 
harvests,  one  of  the  first  facts  he  learns  is  that  it  is  the 
-'limiting  factor"  that  determines  what  the  growth  of 
his  crops  shall  be.  An  exact  definition  of  what  a  limit- 
ing factor  is  would  mean  little  either  to  the  average 
farmer  or  to  you,  but  an  illustration  makes  it  easy  to 
understand  the  meaning  of  the  phrase. 

Suppose  that  in  an  acre  of  land  there  is  enough  nitro- 
gen to  raise  75  bushels  of  corn,  enough  phosphorus  to 
raise  20  bushels,  enough  potassium  and  other  needed 
elements  to  raise  100  bushels,  and  that  the  season  is 
favorable  and  there  are  rain  and  sunshine  enough  to 
make  100  bushels.  What  will  the  crop  be?  It  will  be 
20  bushels. 

The  phosphorus  is  the  limiting  factor  that  makes  it 
impossible  for  the  yield  to  rise  above  that  point.  A 
chain  is  no  stronger  than  its  weakest  link,  and  it  is  not 
the  half  dozen  favorable  factors,  but  the  one  unfavor- 
able one,  that  determines  what  the  harvest  shall  be. 
The  important  thing  for  the  farmer  to  do,  therefore,  is 
to  find  the  factor  that  is  limiting  his  crop  and  strengthen 
the  weak  point.  Otherwise  the  abundant  supply  of 
water  and  of  nitrogen  and  other  plant  foods  in  the  soil 
is  of  no  value  to  him. 

The  limiting  factor  in  health.  The  health  of  the  hu- 
man body  is  dependent  on  many  different  things.  All 
of  these  are  necessary,  and  if  any  one  of  them  is  lacking, 
it  will  be  the  limiting  factor  that  will  make  health  im- 
possible no  matter  how  many  other  conditions  may  be 
favorable.  One  person  may  have  good  food,  fresh  air, 

233 


OTHER  CONSTITU 
TIONAL  DISEASES 
25,334 


CANCER 
,41,039 


DISEASES  OF  STOMACH 


PYOGENIC 
FECTIONS 
26,959 
ENINGITIS 
7.169 


OTHER 
GERM 
ISEASES 
54,527 

ENTERITIS 

(DIARRHEA) 

63,160 


DISEASES 
OF  OTHER 
DIGESTIVE 
8,122 


10.029 
ORGANS 

MEASLES 
6,596 


SCARLET  FEVER 
6.255 


DISEASES  OF  NERVOUS 
SYSTEM  15,365 


DISEASES  OF  ARTERIES 
11,657 

APOPLEXY 
39.701 


BRIGHTS  DISEASE 
47.665 


DYSENTERY 
3.446 


TYPHOID  FEVER 
12,673 

TUBERCULOSIS 
66309 


HEART  DISEASE 
60,047 


ALCOHOLISM 

OLD  AGE          2'909 
13,604 

CHRONIC 
POISONINGS 


PNEUMONIA 
79,524 


INFLUENZA 
7J74 


BRONCHITIS 
12.620 


DEATHS  DURING 
EARLY  INFANCY 
47,386 

SUICIDE     HOMICIDE 
6.590  3,190 


FIG.  148.  Causes  of  deaths  in  1910  estimated  from  Census  reports.  Exact 
figures  cannot  always  be  given.  Pyogenic  infections  are  blood-poisonings  and 
other  inflammations.  This  estimate  covers  58.35  per  cent  of  the  population  in 
sections  where  the  best  conditions  prevail  and  proper  death  records  are  kept. 
The  rate  is  higher  for  the  rest  of  the  country.  Estimates  give  1,450,000  deaths 
in  the  U.S.A.  yearly,  600,000  of  which  are  considered  preventable. 


REALIZING  HEALTH  POSSIBILITIES          235 

and  everything  else  necessary  to  health  except  sufficient 
sleep.  In  other  cases  the  limiting  factor  may  be  the 
condition  of  the  teeth,  adenoids,  lack  of  exercise,  lack  of 
fresh  air,  alcohol,  overwork,  or  improper  food.  With 
many  persons  everything  necessary  for  health  is  present 
if  only  disease  germs  could  be  kept  out  of  the  body. 

In  some  cases  more  than  one  difficulty  must,  of  course, 
be  removed  before  health  can  be  achieved,  but  often 
only  one  factor  makes  the  difference  between  illness 
and  health.  In  our  quest  for  health,  it  is,  therefore, 
most  important  that  we  neglect  none  of  the  factors 
that  are  necessary  for  a  realization  of  our  health  pos- 
sibilities. To  give  you  some  wider  ideas  that  may 
serve  as  guiding  principles  in  your  search  for  limiting 
hygienic  factors  in  your  own  life,  we  shall  in  this  final 
chapter  discuss  in  a  more  general  way  the  causes  of 
sickness  and  how  they  may  be  avoided. 

Two  classes  of  diseases.  Diseases  may  be  divided 
into  two  great  classes,  — germ  diseases  and  what  may 
be  called  physiological  diseases.  In  those  of  the  first 
class,  the  difficulty  is  that  germs  are  growing  in  the 
body  and  poisoning  the  cells.  In  diseases  of  the 
second  class,  the  trouble  is  in  the  body  itself.  Some 
organ  like  the  heart  or  the  liver  fails  in  its  work  and. 
the  body  is  like  an  engine  with  a  broken  part.  Germ 
diseases  are  in  the  main  diseases  of  early  and  middle 
life,  while  physiological  diseases  usually  come  on  only 
in  later  life  when  the  organs  and  tissues  begin  to 
wear  out.  Figure  148  will  give  you  an  idea  of  some  of 
the  more  important  of  the  diseases  belonging  to  each 
of  these  classes. 

The   cause   of   germ   diseases.       Disease    germs    are 


236  PRIMER   OF  PHYSIOLOGY 

either  bacteria,  which  are  very  small  plants,  or  they  are 
little  animals  that  live  in  the  body.  Like  other  living 
things,  germs  must  have  food,  and  they  grow  in  the 
body  because  in  it  they  can  find  the  food  supply  and 
the  warmth  that  they  need.  Unfortunately  for  both 
them  and  us,  however,  disease  germs  produce  toxins  in 
their  bodies  that  poison  our  cells.  These  toxins  throw 
out  of  order  all  the  life  processes  of  the  cells,  and  in 
some  diseases  like  diphtheria  and  scarlet  fever  the  cells 
in  vital  organs  like  the  kidneys  and  the  heart  may  in  a 
very  few  days  become  soft  and.  mucilage-like,  and  many 
of  them  may  undergo  fatty  degeneration  (page  214). 

From  the  diagram  on  page  233  you  will  see  that  germ 
diseases  are  responsible  for  practically  one  half  of  all 
the  deaths  in  the  United  States,  and  they  do  even  more 
damage  than  this  indicates  ;  for  an  attack  of  diphtheria 
at  ten  years  of  age  may  weaken  the  heart  until  it  will 
fail  when  the  person  reaches  fifty  years  of  age,  scarlet 
fever  in  childhood  may  start  trouble  in  the  kidneys  that 
will  lead  to  Bright's  disease  in  later  life,  and  it  is  a  com- 
mon thing  for  typhoid  fever  to  wreck  the  health  for  all 
time.  Insurance  companies  that  have  tried  issuing 
policies  on  the  lives  of  reformed  drunkards  have  found 
the  death  rates  exceedingly  heavy.  Even  when  the 
drinking  is  stopped,  the  effects  of  the  alcohol  that  has 
been  consumed  in  years  past  cannot  be  removed.  So 
even  though  a  person  is  not  killed  outright  by  an  attack 
of  germ  disease,  it  is  nevertheless  true  that  his  cells 
are  often  damaged  by  the  toxins  until  they  never  re- 
cover. Germ  diseases,  therefore,  are  of  far  more  impor- 
tance than  the  mere  number  of  deaths  caused  by  them 
shows. 


REALIZING  HEALTH  POSSIBILITIES          237 

How  the  body  resists  disease  germs.  For  our  resist- 
ance to  many  germs,  we  depend  on  the  white  corpuscles 
of  the  blood,  which  swallow  the  germs  and  destroy  them. 
At  times  the  corpuscles  are  very  active  ;  at  others  they 
seem  to  lose  all  interest  in  germs  and  lie  inactive  when 
the  germs  are  growing  all  about  them.  It  has  been 
found  that  this  difference  in  the  activity  of  the  cor- 
puscles depends  on  whether  or  not  there  are  opsonins 
in  the  blood.  What  these  are  or  where  they  come  from 
is  not  known  exactly,  but  in  some  way  they  seem  to 
make  the  germs  more  appetizing  to  the  corpuscles  and 
cause  the  corpuscles  to  take  them  in.  There  is  a  differ- 
ent opsonin  for  each  different  kind  of  germ,  so  that  one 
may  have  plenty  of  opsonin  for  the  tuberculosis  germ, 
and  little  opsonin  for  the  pneumonia  or  the  grip  germ. 

In  other  diseases  the  germs  are  killed  in  the  body 
by  a  germicidal  substance  which  is  formed  in  the  cells 
and  appears  in  the  lymph  and  the  plasma  of  the  blood. 
This  dissolves  and  kills  the  germs,  and  is  even  more 
important  as  a  defender  of  the  body  than  are  the  white 
corpuscles.  As  in  the  case  of  the  opsonins,  there 
is  a  different  germicidal  substance  for  each  different 
kind  of  germ  that  is  killed  in  this  way.  After  certain 
diseases  the  germicida*!  substances  remain  in  the  blood 
for  years  or  even  for  life,  and  we  usually  suffer  from 
these  diseases  only  once. 

The  relation  of  good  health  to  disease  germs.  The 
power  to  resist  germs  depends  on  having  in  the  blood 
opsonins  and  germicidal  substances  for  the  germs. 
These  are  naturally  present  in  the  blood  of  the  average 
person  only  in  very  small  amounts,  and  merely  being  in 
good  health  does  not  seem  to  increase  these  amounts. 


238  PRIMER   OF  PHYSIOLOGY 

If,  however,  germs  are  introduced  into  the  body,  the 
presence  of  the  germs  causes  the  body  to  begin  the  manu- 
facture of  opsonins  and  germicidal  substances  to  com- 
bat them. 

The  way  to  secure  immunity  to  a  disease,  therefore, 
is  to  have  the  disease,  or  to  introduce  into  the  body 
weak  or  dead  germs  of  the  kind  that  causes  it.  This  is 
what  is  done  in  vaccination  for  smallpox,  typhoid  fever, 
plague,  boils,  catarrh,  and  a  number  of  other  diseases. 
We  cannot  secure  this  immunity  through  good  health 
alone,  as  is  proved  by  the  fact  that  diseases  like  measles, 
typhoid  fever,  cholera,  plague,  smallpox,  and  diphtheria 
attack  the  strong  as  readily  as  they  do  the  weak.1 

It  must  not  be  concluded  from  the  above,  however, 
that  care  of  the  body  is  of  no  importance  in  dealing 
with  germ  diseases.  It  is  true  that  we  cannot  depend 
on  good  health  to  keep  us  from  taking  these  diseases, 
but  after  we  have  them  the  body  has  the  task  of  manu- 
facturing enough  opsonins  and  germicidal  substances  to 
kill  the  germs. 

It  is.  reasonable  to  suppose  that  a  vigorous,  healthy 
body  can  do  this  more  rapidly  than  can  a  feeble  body, 

1  There  is  a  widespread  notion,  even  araong  physicians,  that  if  one 
will  keep  himself  in  good  condition  he  will  be  able  to  "  throw  off "  any 
dangerous  germs  that  may  get  into  his  body.  Unfortunately,  this  theory 
does  nqt  seem  to  be  in  accordance  with  the  facts.  Studies  made  on  the 
soldiers  who  contracted  typhoid  fever  in  the  camp  at  Chickamauga  during 
the  Spanish-American  war  showed  that  these  men  were  no  weaker  than 
those  who  escaped  the  disease,  nor  were  they  sick  or  out  of  condition 
before  the  fever  came  upon  them.  Laboratory  tests  show  that  only  about 
one  fourth  of  the  rats  of  San  Francisco  are  susceptible  to  plague.  There 
is  no  reason  to  believe  that  the  animals  that  take  the  disease  differ  in  any 
way  from  those  that  escape  it,  except  in  their  lack  of  the  germicidal  sub- 
stance which  kills  the  plague  germ. 


REALIZING  HEALTH  POSSIBILITIES  239 

and  even  though  a  strong  body  does  not  protect  us 
from  acute  infections,  it  ought  to  withstand  the  strains 
of  illness  better  than  a  body  that  has  been  weakened 
through  lack  of  care.  Moreover,  in  slow  diseases 
like  tuberculosis,  catarrh,  bronchitis,  chronic  colds,  ma- 
laria, and  chronic  infections  of  many  kinds,  the  body 
has  plenty  of  time  to  manufacture  its  protecting  sub- 
stances, and  a  vigorous  condition  of  the  health  is  of  the 
highest  importance  in  helping  us  combat  ailments  of  this 
kind. 

Nevertheless,  it  remains  true  that  the  way  to  avoid 
germ  diseases  is  to  keep  the  germs  out  of  the  body; 
that  as  long  as  germs  are  allowed  to  be  scattered  about 
they  will  find  millions  of  victims  who  cannot  resist 
them ;  that  the  great  victories  for  health  that  have  been 
won  in  recent  years  have  been  won  mainly  by  prevent- 
ing the  spread  of  infectious  diseases,  and  that  more  can 
yet  be  done  for  the  health  of  the  world  by  fighting 
germs  than  in  all  other  ways  combined. 

Physiological  diseases.  The  causes  of  many  of  the 
ailments  classed  as  physiological  diseases  on  page  233 
are  not  well  understood ;  some  of  them,  like  cancer,  may 
yet  prove  to  be  germ  diseases ;  others  are  due  to  wrong 
chemical  changes  in  the  body  that  as  yet  we  cannot 
remedy ;  a  third  great  group  of  the  most  important  of 
them  are  connected  with  the  degenerative  changes  in 
the  tissues  described  on  page  214,  and  with  other  kinds 
of  degeneration  which  we  shall  not  attempt  to  explain. 

These  degenerative  changes  take  place  most  fre- 
quently of  all  in  the  walls  of  the  arteries  and  in  the 
tissues  of  the  kidneys  and  heart.  Because  of  their 
great  importance  and  because  there  is  hope  that  in  a 


240  PRIMER   OF  PHYSIOLOGY 

measure  at  least  they  can  be  prevented,  we  shall  discuss 
the  causes  of  these  diseases. 

The  causes  of  degeneration  of  the  tissues.  The  de- 
generative changes  in  the  tissues  are  to  be  looked  on  as 
the  wear  and  tear  that  takes  place  in  the  machine. 
They  are  the  same  changes  that  are  found  in  old  age  — 
in  fact,  they  are  old  age.  It  is  probable  that  anything 
that  injures  the  health  of  the  body  in  any  way  hastens 
these  changes,  and  hurries  us  into  old  age  faster  than 
we  otherwise  should  go.  The  following  causes,  how- 
ever, are  agreed  on  by  most  medical  men  as  being  di- 
rectly responsible  for  many  of  these  tissue  changes : 

Ac2ite  infectious  diseases.  After  severe  cases  of  diph- 
theria, scarlet  fever,  measles,  pneumonia,  grip,  meningitis, 
typhoid  fever,  and  other  infections,  degenerative  changes 
have  been  found  in  the  arteries  of  even  young  children. 
With  the  knowledge  that  we  now  have  it  is  possible  to 
prevent  practically  all  of  our  acute  diseases,  and  every 
one  ought  to  be  protected  from  them. 

Chronic  infectious  diseases.  In  the  diagram  on  page 
234,  heart  disease,  Bright's  disease,  and  diseases  of  the 
arteries  are  shown  as  physiological  diseases.  It  would 
perhaps  be  better  to  call  them  germ  diseases ;  for  in 
recent  years  it  has  been  found  that  nearly  all  cases  of 
them  are  caused  by  slow-growing  varieties  of  germs. 
The  two  great  methods  of  defending  ourselves  against 
these  diseases  are  to  give  attention  to  the  teeth,  tonsils, 
nasal  sinuses,  or  other  parts  where  the  germs  have  made 
a  permanent  home,  and  to  live  a  hygienic  life  so  that 
the  resistance  to  the  germs  will  be  built  up. 

Intestinal  toxins.  These  toxins  when  injected  into 
the  blood  of  animals  cause  the  degenerative  changes  in 


REALIZING  HEALTH  POSSIBILITIES          241 

the  tissues  which  we  have  described.  There  is  little 
doubt  that  when  they  are  absorbed  into  the  blood  from 
the  intestines  they  have  the  same  effects,  and  that  they 
are  one  of  the  greatest  of  all  causes  of  the  diseases 
that  we  are  discussing. 

Alcohol.  Users  of  alcohol  suffer  exceedingly  from 
these  changes  in  the  arteries,  kidneys,  and  heart.  The 
effect  of  the  alcohol  often  shows  itself  but  little  until 
middle  life,  when  the  drinker  suddenly  finds  that  the 
organs  which  must  keep  up  the  circulation  of  his  blood 
and  excrete  the  poisons  from  his  body  have  already 
reached  old  age  (see  footnote,  page  213). 

The  possibilities  of  health  and  long  life.  Ninety-five 
per  cent  of  all  human  beings  come  into  the  world  with 
sound  and  healthy  bodies.  Is  it  necessary  that  these 
bodies  shall  suffer  from  disease  ?  There  are  prophets 
of  health  who  look  forward  to  the  day  when  men  shall 
pass  from  birth  to  old  age  without  sickness  or  pain.  Is 
it  necessary  that  our  cells  and  tissues  shall  grow  old  and 
wear  out  ?  Probably,  yes,  but  with  proper  care  of  the 
body  the  passage  of  time  works  comparatively  slight 
changes  in  the  tissues  and  with  the  knowledge  that  we 
now  have  it  would  be  possible  to  extend  the  average 
life  far  beyond  the  limit  that  it  has  yet  reached  in  the 
most  advanced  countries  in  the  world. 

Within  the  lifetime  of  men  and  women  who  are  now 
at  middle  age,  more  has  been  done  to  free  mankind  from 
the  bondage  of  disease  than  was  accomplished  in  all  the 
previous  history  of  the  world.  Still  greater  hygienic 
discoveries  are  almost  in  sight  ahead  of  us,  and  no  one 
can  estimate  the  health  possibilities  that  lie  before  the 
boys  and  girls  of  today.  Three  hundred  years  ago  the 


242  PRIMER   OF  PHYSIOLOGY 

average  human  machine  in  Europe  lasted  twenty  years  • 
today  it  lasts  forty  years  ;  intelligently  cared  for  accord- 
ing to  the  knowledge  that  we  now  have  it  would  prob- 
ably last  seventy  years.  To  what  limit  new  hygienic  dis- 
coveries and  careful  hygienic  living  will  extend  the  life 
of  this  wonderful  machine,  the  future  alone  can  reveal 

QUESTIONS 

Explain  what  is  meant  by  the  limiting  factor  in  crop  raising. 
Discuss  the  limiting  factor  in  health.  Into  what  two  classes 
may  diseases  be  divided  ?  What  is  the  trouble  in  each  case  ? 
Name  some  of  the  more  important  diseases  belonging  to  each 
class. 

What  are  disease  germs  ?  How  do  they  injure  the  body  ? 
What  proportion  of  the  deaths  in  the  United  States  is  due  to 
germ  diseases  ?  What  additional  damage  is  often  done  by 
them? 

In  what  two  ways  are  we  protected  against  germs  ?  What 
are  opsonins?  How  may  the  amount  of  an  opsonin  or  of  a 
germicidal  substance  in  the  blood  be  increased  ?  What  is 
done  in  vaccination  ? 

Is  good  health  sufficient  to  protect  against  germ  diseases  ? 
Give  some  facts  supporting  your  answer.  Why  does  a  strong 
condition  of  the  body  assist  in  recovery  from  germ  diseases  ? 
In  what  kind  of  germ  diseases  is  the  general  health  of  the  body 
especially  important  ?  What  is  the  only  method  of  avoiding 
germ  diseases  ? 

What  organs  of  the  body  are  most  often  affected  by  degen- 
erative changes  in  the  tissues  ?  Give  four  causes  of  these 
changes. 

SUGGESTIONS  TO  THE   TEACHER 

How  to  Live  (Funk  &  Wagnalls),  authorized  by  the  Hygiene  Ref- 
erence Board  of  the  Life  Extension  Institute,  Inc.,  and  prepared  by 
Fisher  and  Fisk,  gives  the  best  available  discussion  of  the  topic- 
treated  in  this  chapter. 


APPENDIX 

The  values  appearing  in  the  last  column  of  the  table  on 
page  244  have  been  secured  by  the  use  of  the  formula  given 
in  Murray's  Economy  of  Nutrition  (Appleton).  This  author 
finds  that  on  an  average  a  pound  of  protein  costs  about  20 
times  as  much  as  a  pound  of  carbohydrate.  The  value  of  a 
food  may  therefore  be  said  to  be  equal  to  the  protein  x  20 
-f  f  at  x  4  -f  carbohydrates.  The  method  of  making  the 
computations  will  be  understood  from  the  following  sample 
problem  in  which  the  relative  values  of  pecans  and  of  an  equal 
weight  of  dried  figs  are  calculated.  Pecans  (as  purchased) 
contain  5.1  per  cent  protein,  37.9  per  cent  fat,  and  8.2  per 
cent  carbohydrates.  Dried  figs  contain  4.3  per  cent  protein, 
.3  per  cent  fat,  and  74.2  per  cent  carbohydrates.  The  rela- 
tive values  of  these  two  foods  may  therefore  be  expressed  by 
the  equation 

5.1  X  20  +  37-9  X  4  +  8.2  =  261.8  = 
4.3  x  20  +  .3  X  4  +  74-2    ""  161.4  ~ 

That  is,  a  pound  of  pecans  ought,  theoretically,  to  sell  in  the 
market  for  1.62  times  as  much  as  a  pound  of  figs.  In  the 
table  on  page  244  the  value  of  bread  is  taken  as  i,  and  the 
other  foods  are  compared  with  it.  The  value  of  any  two 
foods  can  be  compared  in  this  way,  and  it  can  then  be  deter- 
mined which  is  the  cheaper  at  current  market  prices.  The 
teacher  will  understand,  however,  that  in  determining  the  real 
value  of  an  article  of  food  there  may  be  many  factors  not 
taken  into  account  in  the  above  formula.  Bulletin  No.  28  of 
the  United  States  Department  of  Agriculture  contains  a  very 
complete  list  of  analyses  showing  the  chemical  composition  of 
American  foodstuffs.  It  is  sold  by  the  Superintendent  of 
Public  Documents,  Washington,  D.C.,  for  five  cents. 

243 


244 


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PRONOUNCING  GLOSSARY 


abdomen  (ab-do'men). 
abdominal  (ab-dom'i-nal). 
adenoid  (ad'en-oid). 
Agave  (a-gah've). 
amylopsin  (a-ml-16p'sin). 
aqueous  (a'que-us). 
astigmatism  (as-tlg'mat-ism) . 
auricle  (o'ri-cl). 
bacterium  (bak-te'ri-um). 
beriberi  (beV  i-ber'i) . 
bronchial  (brong'ke-al). 
bronchitis  (brong-kl'tis). 
canine  (ka-mn')- 
capillary  (cap'il -la-re), 
cerebellum  (ser-e-bel'lum). 
cerebrum  (ser'e-brum). 
choroid  (ko'roid). 
chloral  (klo'ral). 
cocain  (ko'ka-In). 
coccyx  (kok'six). 
cochlea  (kok'le-a). 
cornea  (kor'ne-a). 
corpuscle  (kor'pusl). 
dentine  (den 'tin). 
diaphragm  (di'a-fram). 
diphtheria  (dif-the'ri-a). 
enzyme  (en'zlm). 
esophagus  (e-sof  a-gus) . 
Eustachian  (yu-stak'ke-an) . 
femur  (fe'mur). 
fertilization  (fer-til-Tz-a'shun) . 
germicidal  (jer-mi-si'dal). 
glycogen  (gli'ko-jen). 
incisor  (in-si'sor). 
hasheesh  (hash-esh'). 
hemoglobin  (hem-6-glo  'bin) . 
humerus  (hyu'me-rus) . 
humidifier  (hyu-mld'i-fi-er). 
hygiene  (hi'ji-en  or  hi'jen). 


hygienic  (hl-je-en'ik). 
lipase  (llp'as). 
lymphatic  (iim-fat'ik) . 
magnesium  (mag-ne'zhe-um). 
medulla  oblongata  (med-ul'la  6b« 

lon-gah'ta). 
molar  (mo'lar). 
narcotic  (nar-kot'ic). 
nicotin  (nlkfo-tln). 
opsonin  (6p's5-nln). 
pancreas  (pan'kre-as). 
papilla  (pap-il'ah). 
patella  (pa-tel 'la), 
pepsin  (pep'sin). 
permanganate  (per-man'gan-5t). 
phalanges  (fa-lan'jez) . 
pollen  (pol'len). 
polyp  (pol'ip).  ^ 
protein  (pro'te-in). 
protoplasm  (pro'to-plasm). 
ptyalin  (tl'a-lin). 
respiratory  (res'pl-ra-to-re) . 
retina  (ret'i-na). 
saliva  (sal-I'vah). 
salivary  (sal'i-va-re). 
sciatic  (sT-at'ik). 
sclerotic  (skle-rot'ik). 
sepal  (sep'l). 
stamen  (sta'men). 
strychnin  (strlk'nln). 
tonsillitis  (ton-sll-li'tis). 
trachea  (tra'ke-a). 
trachoma  (tra-ko'ma). 
trypsin  (trlp'sin). 
tympanic  (tlm-pan'ik). 
tympanum  (tlmrpan-um). 
ureter  (yu-re'ter). 
vitreous  (vlt're-us). 


246 


INDEX 


A  star  (*)  after  a  page  number  indicates  that  an  illustration  of  the  subject  appears  on 
that  page. 


Accidents,  221,*  222,*  223,*  224- 
225,*  226-229,*  230-231. 

Accommodation,  of  eye,  114,  115. 

Adenoids,  73,*  74,*  75,*  76,  77- 

Agave,  juice  of,  211. 

Air,  impurities  of,  57 ;  importance 
of  fresh,  60,*  61,  62,*  63;  rela- 
tion to  respiration,  54;  gaseous 
impurities  in,  57 ;  composition  of, 
6 1 ;  dry,  injurious,  63* ;  neces- 
sity for  motion  in,  64-66;  rela- 
tion to  nervous  system,  105. 

Alcohol,  89,  210-221 ;  source  of, 
211 ;  effect  on  health  and  length 
of  life,  212;  on  cells,  214;  on 
mind,  216-218;  on  muscles,  218- 
219;  on  digestion,  155;  on 
strength,  218;  as  a  food,  162- 
164;  on  heart,  50;  permanent 
effects,  235. 

Alexander  the  Great,  5.* 

Alimentary  canal,  146. 

Ammo-acids,  167. 

Amylopsin  (an  enzyme) . 

Antidotes  for  common  poisons,  231. 

Appendix,  vermiform,  146,*  150. 

Arteries,  40,  41*,  43,  47,*  214,  224, 
241. 

Astigmatism,  115,  118. 

Auricles,  41,*  42,  43.* 

Bacteria,  154,  155,  235. 
Bandages,  how  applied,  23,*  222,* 

223.* 

Bathing,  78,  8 1,  87,  88. 
Bicuspids,  187,  189.* 
Bile,  150,  151,*  152. 
Bleeding,  treatment  of,  224.* 
Blood,  function  of,  40 ;   circulation 

of,  40,  41,*  42,  43,*  44,  45,*  46. 

See  also  Corpuscles,  Lymph,  and 

Plasma. 
Blood  vessels,  40,  41,*   42,*  43*; 

effect  of  alcohol  on,  50. 
Body,  growth  from  single  cell,  n*; 


keeping  in  repair,  14 ;  framework 
of,  16-23;  carriage  of,  3i*~37; 
and  health,  107. 

Body  heat,  how  regulated,  84,*  85  ; 
danger  of  overheating,  86;  rela- 
tion to  alcohol,  89. 

Bones.     See  Skeleton, 

Brain,  92.;  structure  and  functions 

of,  93,  94,*  95-*     . 
Bronchial  tubes,  54,  56. 
Bronchitis,  81. 
Burbank,  Luther,  203. 
Burns,  treatment  of,  225. 

Calcium,  140. 
Cancer,  of  throat,  58,  205. 
Capillaries,  40,  45,  153. 
Carbohydrates,  138,  159,  161,  175, 

176. 
Carbon  dioxid,  13,  54,  55,  62,  159, 

211. 

Cartilage,  21. 
Catarrh,  81. 
Cells  of  human  body,  7-10,*  n,* 

12*;  effect  of  alcohol  on,  214;  of 

plants,  7,  ib.* 
Cerebellum,  95.* 
Cerebrum,  94,*  95.* 
Chloral,  199. 

Choroid  coat  of  eye,  in,  113. 
Cocain,  199. 
Coccyx,  17,*  1 8. 
Colds,  cause  of,  76;   remedies  for, 

77-79;    effect  of  drafts  on,  79; 

chronic,  81. 
Cornaro,  Louis,  5.* 
Corpuscles,   44;    function   of    red, 

44 ;  function  of  white,  44,  79. 
Crypt,  73-* 

Dennis,  84.* 

Diaphragm,  54.* 

Diet,  low-protein,  167-170;  high- 
protein,  170-173 ;  advantages  of 
mixed,  174;  sample,  174,  175. 


247 


248 


INDEX 


Digestion,  145-157;  organs  of, 
146,*  147,*  148,*  149,  151,*  154. 
juices  of,  148-152;  process  of, 
151-155  ;  effect  of  alcohol  on,  155. 

Disease,  prevention  of,  3 ;  preva- 
lence through  ignorance,  4,*  5 ; 
resistance  of  body  to,  237. 

Disease  germs,  how  body  resists, 
237 ;  relation  of  good  health  to, 
237-239  J  effect  on  heart,  47 ;  of 
chronic  colds,  77 ;  of  appendi- 
citis, 150;  of  typhoid,  4.* 

Diseases,  some  caused  by  alcohol, 
215 ;  classes  of,  235 ;  cause  of 

.  germ,  235,  236;  constitutional, 
239 ;  infectious,  240. 

Dislocations,  22. 

Drowning,  treatment  of  apparent, 
226,*  227. 

Dust,  effect  on  respiration,  56,* 
57-* 

Ear,  122-128;  function  of,  122,* 
123;  structure  of,  123,*  124,* 
125*;  care  of,  126,  127.* 

Electric  fans,  65. 

Electricity,  dangers  from,  227,  228. 

Enamel,  of  teeth,  184.* 

Enzymes,  147-153. 

Epidermis,  84.* 

Esophagus,  148,  152. 

Eustachian  tube,  72,*  123,*  126. 

Exercise,  effects  on  heart,  48 ;  forms 
of,  49 ;  as  aid  to  digestion,  178. 

Eye,  109-121 ;  structure,  no,  in,* 
112,*  113*;  accommodation  of, 
114,115;  care  of,  116,*  119,*  120; 
effect  of  disease  germs  on,  118; 
foreign  bodies  in,  228. 

Far-sightedness,  115. 

Fats,  as  food,  138,  150,  151,*  161,* 

162,  176. 
Femur,  17,*  19. 
Fermentation,  211. 
Fibula,  17,*  20. 
Fletcher,  Horace,  156. 
Flowers,  parts  of,  8, 9* ;  fertilization, 

of  egg,  10. 
Follicles,  85. 


Foods,  135-144;  function  of,  135,* 
136,*  175;  absorption  of,  153, 
154* ;  classes  of,  138 ;  selection  of, 
143 ;  importance  of  mastication 
of,  155;  and  health,  166-181; 
cost  of,  177. 

Foot,  relation  to  carriage  of  body, 
33,*  34,  35-* 

Gastric  glands  and  juice,  149,  152, 

155- 

Germicidal  substance  in  blood,  237. 
Germs.     See  Disease  Germs. 
Gladstone,  156. 
Glycogen,  161. 

Headache  remedies,  49. 

Hearing,  109.     See  also  Ear. 

Heart,  40-50;  structure  of,  41,* 
42,*  43* ;  care  of,  46 ;  effect  of 
disease  germs  on,  47 ;  effect  of 
exercise  on,  49 ;  effect  of  tobacco 
on,  49 ;  of  headache  remedies  on, 
49;  effect  of  alcohol  on,  50,  241. 

Hemoglobin,  140. 

Humerus,  17,*  19. 

Humidifier,  63.* 

Incisors,  186,  187,  188,*  189.* 

Incus,  124.* 

Intestines,  146,*  14,9, 150, 151,*  153, 

I54-* 

Iris,  112,*  113.* 
Iron,  in  food,  140,  142,  143. 

Joints,  2i.* 

Kidneys,  13,  160,*  241. 

Ligaments,  21.* 

Life,  average  length  of,  i,  2* ;    laws 

of,  5 ;  effect  of  alcohol  on  length 

of,  212. 

Lime,  in  food,  140. 
Limiting  factor,  in  health,  233. 
Lipase,  (an  enzyme). 
Liver,  146,*  150. 
Lymph,  cells  bathed  by,  12,  45*; 

necessary  for  health  of  cells,  12, 

13;   function  of,  45,  46. 
Lymphatic  vessels,  46.* 


INDEX 


249 


Malleus,  124.* 

Mastication,  importance  of,  155. 

Mastoid  cavity,  123,*  124. 

Mastoiditis,  124. 

Medulla,  94,*  96. 

Metacarpals,  17,*  20. 

Metatarsals,  17,*  20. 

Milk,  as  a  food,  140,  142.     See  also 

Carbohydrates. 
Mind,  peaceful,  necessary  to  health, 

106-108;    effect  of  tobacco  on, 

203;     effect  of  alcohol  on,  216- 

218. 
Minerals,  needed  by  body,  139-142  ; 

foods  rich  in,   142 ;    in  protein 

foods,  172. 

Molars,  186,  187,  188,*  189,*  190.* 
Muscles,  function  of,  26,*  27,*  28,* 

29,*  30*;  structure  of,  27. 

Near-sightedness,  115,  118. 

Nerves,  92;  cells  of,  92,  93*;  fibers 
of,  93*;  sciatic,  93. 

Nervous  system,  91-100;  structure 
of,  9i*~93*,  94-96;  function  of, 
92,  97,*  98-100;  care  of,  102*- 
104,*  105,  106,*  108. 

Nicotin,  199,  200,  206.  See  also 
Tobacco, 

Nose,  structure  of,  70,  71*;  func- 
tion of,  71 ;  troubles  of,  71,  72, 
77 ;  foreign  bodies  in,  229. 

Opsonins,  237. 

Oxygen,  13,  44,  55,  61,  64. 

Pancreas,  146,*  150. 

Pancreatic  juice,  150. 

Patella,  17,*  20. 

Pellagra,  154,  156. 

Pelvic  bones,  17,*  19. 

Pepsin,  149,  151,*  152,  153. 

Phalanges,  17,*  20. 

Phosphorus,  138,  140,  141. 

Physiological  diseases,  234.* 

Poisoning,  treatment  for,  230,*  231. 

Proteins,  138,  148,  151,*  159,  161, 

166,  167,*  168,  169,*  170-174. 
Ptyalin  (an  enzyme). 
Quinine,  126. 


Reflex  actions,  96,  97,*  98-100. 
Respiration,  53-58;   objects  of,  53, 

54;    organs   of,    54,*    55,*    56*; 

effect  of  dust  on,  56,*  57*;  effect 

of  tobacco  on,  58. 

Rest,  relation  to  nervous  system,  104. 
Retina,  in,  112,*  113,  115,  117. 
Ribs,  17,*  18,*  19. 
Rickets,  154-155- 

Sacrum,  17,*  19. 

Saliva,  148,  151,*  152. 

Salivary  glands,  146,  147,  148.* 

Scapula,  19. 

Schools,  open-air,  62,*  66,*  67,*  68,* 

105. 

Scurvy,  1547155- 
Shoes,  relation  to  carriage  of  the 

body,  and  to  health,  33,*  34,* 

35,*  36,*  37-* 
Sickness,  possibilities  of  preventing, 

3,*  4,*  239. 
Skeleton,  function  of,  16, 17* ;  parts 

of,  i8*-2i. 
Skin,  function  of,  84,  85 ;  structure, 

84,*  85. 

Skull,  17,*  18.* 
Sleep,   importance  of,    102,*    103; 

out-of-door,  68,  105. 
Smell,  function  of,  132 ;    organ  of, 

132*;  care  of  organ  of,  133.     See 

also  Nose. 
Special  senses,  109.     See  also,  Eye, 

Ear,  Hearing,  Smell,  Taste,  Touch, 

Vision. 

Spectacles,  116. 
Spinal  column,  17*;    structure  of, 

18*;   support  of,  29,*  30;   func- 
tion of,  31-33. 
Spinal  cord,  91,*  92,  96. 
Sprains,  treatment  of,  22. 
Stapes,  124.* 
Sternum,  17,*  19. 
Stomach,  13,  50,  147,*  148,  151,* 

i52- 
Sugar,  grape,  153,  175;   as  a  food, 

175,176.     See  also  Carbohydrates. 
Sweat  glands,  84,*  85. 

Tartar,  on  teeth,  191. 


250 


INDEX 


Taste,  109,  132. 

Teeth,  146,  183-196  ;  structure, 
184*;  care  of,  182,  183,  185,* 
187,*  188-194;  permanent,  1 86,* 
189,*  190*;  temporary,  187,* 
188,*  190.* 

Tendons,  27,  28.* 

Throat,  72,*  73,*  74^76;  foreign 
bodies  in,  229. 

Tibia,  17,*  20. 

Tobacco,  i97*-209;  a  drug,  199; 
influence  on  growth,  200-202 ; 
effect  on  heart,  49;  effect  on 
respiratory  organs,  58 ;  effect  on 
muscles,  202 ;  effect  on  nervous 
system,  202 ;  effect  on  the  mind, 
204;  effect  of  moderate  use  of, 
206;  why  a  boy  should  not  use, 
207. 

Tonsils,  structure  of,  72,*  73; 
diseases  of,  73,*  74* ;  remedy  for, 

75- 
Touch,    function    and    organs    of, 

129,*  130,*  131. 
Toxins,  154;    intestinal,  170,  178, 

179,  240. 


Trachea,  54,  55.* 
Trachoma,  118. 
Trypsin,  (an  enzyme) . 
Tympanic  membrane,  124.* 

Valves,  of  heart,  41,*  42,  43,*  47, 
of  arteries,  47* ;  of  veins,  48.* 

Veins,  40,  48.* 

Ventilation,  60-69  >  necessity  for, 
60,*  61,*  64;  open-air  schools, 
65,*  66,*  67,*  68;  open-air 
sleeping,  60,*  68. 

Ventricles,  41,*  42,  43.* 

Vermiform  appenolix,  146,*  150. 

Vertebra,  18.* 

Vim,  149. 

Vision,  testing,  117,*  121;  defects 
of,  115,  116.  See  also  Eye. 

Vitamins,  143-144. 

Windows,  in  schools,  119. 
Wounds,  care  of,  223,  224.* 

Yeast,  211. 


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